Genetic Counseling Program Overview – School of Medicine

IMPORTANT: APPLICATION DEADLINE IS NOWDECEMBER 15THGENETIC COUNSELING TRAINING PROGRAMIntroduction and Program Goals

The Genetic Counseling Training Program, leading to a Master of Science degree in Genetic Counseling, is a two-year academic program comprised of didactic course work, laboratory exposure, research experience and extensive clinical training. The program, directed by Anne L. Matthews, R.N, Ph.D., is an integral component of the teaching and research programs in the Department of Genetics and Genome Sciences (G&GS) at CWRU under the leadership of Dr. Anthony Wynshaw-Boris, MD. Ph.D., chairman of G&GS. Program leadership also includes Rebecca Darrah, MA, MS, PhD, Associate Director and the program’s medical director, Shawn McCandless M.D., Associate Professor of G&GS and Pediatrics and Director of the Center for Human Genetics, University Hospitals Cleveland Medical Center. The Program is accredited by the Accreditation Council for Genetic Counseling (ACGC) and graduates of the program are eligible to apply for Active Candidate Status and sit for the American Board of Genetic Counseling certification examination.

The overall objective of the Genetic Counseling Program is to prepare students with the appropriate knowledge and experiences to function as genetic counselors in a wide range of settings and roles. With unprecedented advances in our understanding of the genetic and molecular control of gene expression and development, and in our ability to apply this knowledge clinically, the Program strives to train students who can interface between patients, clinicians and molecular and human geneticists. Students gain insightful and multifaceted skills that will enable them to be effective genetic counselors, aware of the many new technical advances and often-difficult ethical, legal and social issues that have surfaced in the light of the Human Genome Project. Graduates of the Program will be prepared to work in a variety of settings including both adult and pediatric genetics clinics, specialty clinics such as cancer genetics, cardiovascular genetics and metabolic clinics, and prenatal diagnosis clinics, as well as in areas of research or commercial genetics laboratories relevant to genetic counseling and human genetics.

A unique aspect of the Genetic Counseling Training Program that it is housed within Case Western Reserve’s Department of Genetics and Genome Sciences that is internationally known for both its clinical expertise and cutting edge research in molecular genetics, model organisms and human genetics. Thus, the Department of G&GS at CWRU provides an interface between human and medical genetics with basic genetics and provides an exciting atmosphere in which to learn and develop professionally. The direct access to both clinical resources and advanced technologies in human and model organisms affords students with an unparalleled environment for achievement. The Graduate Program in Genetics in the Department of Genetics and Genome Sciences provides an interactive and collaborative environment for both pre (genetic counseling and PhD students) – and post-doctoral trainees to come together in a collegial atmosphere. By fostering interactions between pre- and post-doctoral trainees in genetic counseling, medical genetics, and basic research at an early stage of their careers, it is anticipated that graduates will be well-rounded professionals with an understanding of the importance of both clinical and basic research endeavors. Moreover, such resources as the Department of Biomedical Ethics, the Center for Genetic Research, Ethics and Law, the Mandel School of Applied Social Sciences, and the Law-Medicine Center provide for an enriched learning experience for students.

The curriculum consists of 40 semester hours: 22 semester hours of didactic course work and 7 semester hours of research. Additionally, there are four 8-week clinical rotations, one 3-week laboratory rotation and one 6-week summer clinical rotation required of all students, which provide an additional 11 credit hours. Courses include material covering basic genetics concepts, embryology, medical genetics, biochemical genetics, molecular genetics, cytogenetics, genomics, cancer genetics, population genetics, genetic counseling principles, human development, psychosocial issues, interviewing techniques, and ethical and professional issues in genetic counseling.

Clinical rotations include one intensive three-week laboratory rotation in diagnostic cytogenetics and clinical molecular genetics as well as the Maternal Serum Screening program. There are four 8-week clinical rotations during year 2 during which students obtain clinical experience in General Genetics (children and adults) including Specialty Clinics such as Marfan Clinic, Prader-Willi Clinic and Craniofacial Clinic; Prenatal Diagnosis Clinic, and Cancer Genetics Clinic. These rotations take place at The Center for Human Genetics at University Hospitals Cleveland Medical Center, the Genomic Medicine Institute at the Cleveland Clinic and MetroHealth Medical Center. Students also will have the opportunity to pursue an elective rotation with specialty clinics or intern with genetic counselors in such areas as commercial testing companies. Additionally, there is one off-site rotation – a 6-week clinical rotation which is held at Akron Children’s Hospital in Akron Ohio during the summer. Moreover, students rotate through the Cleveland-based institutions for weekly observational experiences starting early in year 1 of the program.

Students are also required to attend and participate in a number of other activities such as weekly Clinical Patient Conferences, Genetics Grand Rounds, Departmental Seminars and Journal Club. Students also participate with the doctoral graduate students in the Department of Genetics and Genome Sciences’ annual retreat and present their research projects during the poster sessions. In addition, counseling students present their research during the program’s Research Showcase. Students also have an opportunity to give educational talks to local schools, participate in DNA Day at local high schools and other groups when available.

Tuition for the 2017-2018 academic year is $1,827.00 per semester hour. Currently, other fees include student health insurance ($986 per semester) and a student activity fee of $14.00 per semester.

The Department of Genetics is unable to provide financial aid or research/teaching assistantships to students; however, it does award some scholarship funding in the form of a monthly stipend to genetic counseling students. The amount of the stipend is determined yearly and will be shared with applicants at the time of their interviews. In addition, the costs of the on-line embryology course as well as the CWRU Technology fee of $852.00 per year are covered by the Department. Moreover, students receive funds to cover the costs associated with their research projects and second year students receive funds to travel to the National Society of Genetic Counselors’ annual education conference held in the fall.

Financial aid is available to graduate students. The university has extensive information regarding financial aid and scholarship opportunities to assist students in funding their education. For additional information or assistance, please contact the Office of University Financial Aid at http://case.edu/stage/admissions/financialaid.html or (216) 368-4530.

Clarice Young at (216) 368-3431 or email: clarice.young@case.edu

OR

The Program Director:

Please Note: The Direct Application link will take you to the School for Graduate Studies webpage. Go to Prospective Students – Admissions Information – Graduate Program Applications. You will see a link on the right hand side of the page entitled Application Log In to begin your application.

The application includes:

Fulfillment of the requirements for admission to the School of Graduate Studies at Case Western Reserve University must be met as well as those required by the Genetic Counseling Training Program. An applicant having graduated with excellent academic credentials (minimum undergraduate grade point average of 3.0 on a 4.0 scale) from a fully accredited university or college. Complete credentials must be on file with the School of Graduate Studies.

The Genetic Counseling Training Program at Case Western Reserve University is participating in the Genetic Counseling Admissions Match through National Matching Services (NMS) beginning with admissions for Fall 2018. The GC Admissions Match has been established to enhance the process of placing applicants into positions in masters-level genetic counseling programs that are accredited by the Accreditation Council for Genetic Counseling (ACGC). The Match uses a process that takes into account both applicants’ and programs’ preferences. All applicants must first register for the Match with NMS before applying to participating genetic counseling graduate programs. At the conclusion of all program interviews, both applicants and programs will submit ranked lists of preferred placements to NMS according to deadlines posted on the NMS website. The binding results of the Match will be released to both applicants and programs simultaneously in late April.

Please visit the NMS website at (https://natmatch.com/gcadmissions) to register for the match, review detailed information about the matching process, and to view a demonstration of how the matching algorithm works.

Important: After you have registered with NMS, you will need to put your NMS ID number at the top of your CV/Resume and/or at the top of your personal statement.

The average GPA for matriculating students is 3.5 and GRE mean scores are approximately, 60-70th percentiles and above. However, we take a holistic view of the applicant’s complete file in determining admission, which means we look at everything the applicant has submitted. A high GPA or GRE score will not automatically lead to admission; neither will low scores automatically lead to a denial.*While the CWRU application form asks for your GRE scores, please include the percentile score as well.

The Personal Statement is extremely important and applicants need to pay specific attention to how they present themselves in their Personal Statement. Aspects to remember include: Is the applicant’s Personal Statement grammatically sound, and does it give us a clear picture as to who the applicant is? Applicants’ should emphasize those experiences which have directly assisted them in becoming aware of and knowledgeable about the genetic counseling profession. Genetic counselors are highly motivated and hardworking individuals. Thus, the Admissions Committee looks for applicants who demonstrate initiative, self-direction, excellent communication skills and who have “gone the extra mile” to show their passion for becoming a genetic counselor.

Letters of recommendation should be written by individuals who can provide an accurate picture of your academic capabilities, your communication skills (both written and spoken) and your potential to successfully complete graduate education. At least two referees should be faculty from your past institutions. Other excellent referee sources include genetic counselors you have shadowed or supervisors of internships or advocacy experiences which you have had. Recommendation letters from friends or family members are discouraged. Please note, while CWRU provides an on-line recommendation form for referees to complete, your referee should also provide a personal letter to accompany the form.

While the number of applications received by the Program varies from year to year, in general we receive approximately 60 – 70+ applications each year. At this time, the Program is able to accept 8 students per year.

December 15th of each year is the application deadline. It is important that all required materials such as GRE scores (including their percentiles), transcripts from all institutions in which you have completed coursework and letters of reference be submitted by the application deadline if you wish to have your application reviewed by the Admissions Committee. If you will be taking a prerequisite course or courses in the upcoming semester that will not be reflected on your current transcripts, please let us know in your personal statement (or Resume) which course or courses you will be taking to meet the pre-requisites. Also, please submit a current CV or resume along with your personal statement. The Program only admits one class per year — in fall semester. Because of the intensive nature of the Program, all students must be full time, we are unable to accommodate part-time students.

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Genetic Counseling Program Overview – School of Medicine

Hedonism | Internet Encyclopedia of Philosophy

The term “hedonism,” from the Greek word (hdon) for pleasure, refers to several related theories about what is good for us, how we should behave, and what motivates us to behave in the way that we do. All hedonistic theories identify pleasure and pain as the only important elements of whatever phenomena they are designed to describe. If hedonistic theories identified pleasure and pain as merely two important elements, instead of the only important elements of what they are describing, then they would not be nearly as unpopular as they all are. However, the claim that pleasure and pain are the only things of ultimate importance is what makes hedonism distinctive and philosophically interesting.

Philosophical hedonists tend to focus on hedonistic theories of value, and especially of well-being (the good life for the one living it). As a theory of value, hedonism states that all and only pleasure is intrinsically valuable and all and only pain is intrinsically not valuable. Hedonists usually define pleasure and pain broadly, such that both physical and mental phenomena are included. Thus, a gentle massage and recalling a fond memory are both considered to cause pleasure and stubbing a toe and hearing about the death of a loved one are both considered to cause pain. With pleasure and pain so defined, hedonism as a theory about what is valuable for us is intuitively appealing. Indeed, its appeal is evidenced by the fact that nearly all historical and contemporary treatments of well-being allocate at least some space for discussion of hedonism. Unfortunately for hedonism, the discussions rarely endorse it and some even deplore its focus on pleasure.

This article begins by clarifying the different types of hedonistic theories and the labels they are often given. Then, hedonisms ancient origins and its subsequent development are reviewed. The majority of this article is concerned with describing the important theoretical divisions within Prudential Hedonism and discussing the major criticisms of these approaches.

When the term “hedonism” is used in modern literature, or by non-philosophers in their everyday talk, its meaning is quite different from the meaning it takes when used in the discussions of philosophers. Non-philosophers tend to think of a hedonist as a person who seeks out pleasure for themselves without any particular regard for their own future well-being or for the well-being of others. According to non-philosophers, then, a stereotypical hedonist is someone who never misses an opportunity to indulge of the pleasures of sex, drugs, and rock n roll, even if the indulgences are likely to lead to relationship problems, health problems, regrets, or sadness for themselves or others. Philosophers commonly refer to this everyday understanding of hedonism as “Folk Hedonism.” Folk Hedonism is a rough combination of Motivational Hedonism, Hedonistic Egoism, and a reckless lack of foresight.

When philosophers discuss hedonism, they are most likely to be referring to hedonism about value, and especially the slightly more specific theory, hedonism about well-being. Hedonism as a theory about value (best referred to as Value Hedonism) holds that all and only pleasure is intrinsically valuable and all and only pain is intrinsically disvaluable. The term “intrinsically” is an important part of the definition and is best understood in contrast to the term “instrumentally.” Something is intrinsically valuable if it is valuable for its own sake. Pleasure is thought to be intrinsically valuable because, even if it did not lead to any other benefit, it would still be good to experience. Money is an example of an instrumental good; its value for us comes from what we can do with it (what we can buy with it). The fact that a copious amount of money has no value if no one ever sells anything reveals that money lacks intrinsic value. Value Hedonism reduces everything of value to pleasure. For example, a Value Hedonist would explain the instrumental value of money by describing how the things we can buy with money, such as food, shelter, and status-signifying goods, bring us pleasure or help us to avoid pain.

Hedonism as a theory about well-being (best referred to as Prudential Hedonism) is more specific than Value Hedonism because it stipulates what the value is for. Prudential Hedonism holds that all and only pleasure intrinsically makes peoples lives go better for them and all and only pain intrinsically makes their lives go worse for them. Some philosophers replace “people” with “animals” or “sentient creatures,” so as to apply Prudential Hedonism more widely. A good example of this comes from Peter Singers work on animals and ethics. Singer questions why some humans can see the intrinsic disvalue in human pain, but do not also accept that it is bad for sentient non-human animals to experience pain.

When Prudential Hedonists claim that happiness is what they value most, they intend happiness to be understood as a preponderance of pleasure over pain. An important distinction between Prudential Hedonism and Folk Hedonism is that Prudential Hedonists usually understand that pursuing pleasure and avoiding pain in the very short-term is not always the best strategy for achieving the best long-term balance of pleasure over pain.

Prudential Hedonism is an integral part of several derivative types of hedonistic theory, all of which have featured prominently in philosophical debates of the past. Since Prudential Hedonism plays this important role, the majority of this article is dedicated to Prudential Hedonism. First, however, the main derivative types of hedonism are briefly discussed.

Motivational Hedonism (more commonly referred to by the less descriptive label, “Psychological Hedonism”) is the theory that the desires to encounter pleasure and to avoid pain guide all of our behavior. Most accounts of Motivational Hedonism include both conscious and unconscious desires for pleasure, but emphasize the latter. Epicurus, William James, Sigmund Freud, Jeremy Bentham, John Stuart Mill, and (on one interpretation) even Charles Darwin have all argued for varieties of Motivational Hedonism. Bentham used the idea to support his theory of Hedonistic Utilitarianism (discussed below). Weak versions of Motivational Hedonism hold that the desires to seek pleasure and avoid pain often or always have some influence on our behavior. Weak versions are generally considered to be uncontroversially true and not especially useful for philosophy.

Philosophers have been more interested in strong accounts of Motivational Hedonism, which hold that all behavior is governed by the desires to encounter pleasure and to avoid pain (and only those desires). Strong accounts of Motivational Hedonism have been used to support some of the normative types of hedonism and to argue against non-hedonistic normative theories. One of the most notable mentions of Motivational Hedonism is Platos Ring of Gyges example in The Republic. Platos Socrates is discussing with Glaucon how men would react if they were to possess a ring that gives its wearer immense powers, including invisibility. Glaucon believes that a strong version of Motivational Hedonism is true, but Socrates does not. Glaucon asserts that, emboldened with the power provided by the Ring of Gyges, everyone would succumb to the inherent and ubiquitous desire to pursue their own ends at the expense of others. Socrates disagrees, arguing that good people would be able to overcome this desire because of their strong love of justice, fostered through philosophising.

Strong accounts of Motivational Hedonism currently garner very little support for similar reasons. Many examples of seemingly-pain-seeking acts performed out of a sense of duty are well-known from the soldier who jumps on a grenade to save his comrades to that time you rescued a trapped dog only to be (predictably) bitten in the process. Introspective evidence also weighs against strong accounts of Motivational Hedonism; many of the decisions we make seem to be based on motives other than seeking pleasure and avoiding pain. Given these reasons, the burden of proof is considered to be squarely on the shoulders of anyone wishing to argue for a strong account of Motivational Hedonism.

Value Hedonism, occasionally with assistance from Motivational Hedonism, has been used to argue for specific theories of right action (theories that explain which actions are morally permissible or impermissible and why). The theory that happiness should be pursued (that pleasure should be pursued and pain should be avoided) is referred to as Normative Hedonism and sometimes Ethical Hedonism. There are two major types of Normative Hedonism, Hedonistic Egoism and Hedonistic Utilitarianism. Both types commonly use happiness (defined as pleasure minus pain) as the sole criterion for determining the moral rightness or wrongness of an action. Important variations within each of these two main types specify either the actual resulting happiness (after the act) or the predicted resulting happiness (before the act) as the moral criterion. Although both major types of Normative Hedonism have been accused of being repugnant, Hedonistic Egoism is considered the most offensive.

Hedonistic Egoism is a hedonistic version of egoism, the theory that we should, morally speaking, do whatever is most in our own interests. Hedonistic Egoism is the theory that we ought, morally speaking, to do whatever makes us happiest that is whatever provides us with the most net pleasure after pain is subtracted. The most repugnant feature of this theory is that one never has to ascribe any value whatsoever to the consequences for anyone other than oneself. For example, a Hedonistic Egoist who did not feel saddened by theft would be morally required to steal, even from needy orphans (if he thought he could get away with it). Would-be defenders of Hedonistic Egoism often point out that performing acts of theft, murder, treachery and the like would not make them happier overall because of the guilt, the fear of being caught, and the chance of being caught and punished. The would-be defenders tend to surrender, however, when it is pointed out that a Hedonistic Egoist is morally obliged by their own theory to pursue an unusual kind of practical education; a brief and possibly painful training period that reduces their moral emotions of sympathy and guilt. Such an education might be achieved by desensitising over-exposure to, and performance of, torture on innocents. If Hedonistic Egoists underwent such an education, their reduced capacity for sympathy and guilt would allow them to take advantage of any opportunities to perform pleasurable, but normally-guilt-inducing, actions, such as stealing from the poor.

Hedonistic Egoism is very unpopular amongst philosophers, not just for this reason, but also because it suffers from all of the objections that apply to Prudential Hedonism.

Hedonistic Utilitarianism is the theory that the right action is the one that produces (or is most likely to produce) the greatest net happiness for all concerned. Hedonistic Utilitarianism is often considered fairer than Hedonistic Egoism because the happiness of everyone involved (everyone who is affected or likely to be affected) is taken into account and given equal weight. Hedonistic Utilitarians, then, tend to advocate not stealing from needy orphans because to do so would usually leave the orphan far less happy and the (probably better-off) thief only slightly happier (assuming he felt no guilt). Despite treating all individuals equally, Hedonistic Utilitarianism is still seen as objectionable by some because it assigns no intrinsic moral value to justice, friendship, truth, or any of the many other goods that are thought by some to be irreducibly valuable. For example, a Hedonistic Utilitarian would be morally obliged to publicly execute an innocent friend of theirs if doing so was the only way to promote the greatest happiness overall. Although unlikely, such a situation might arise if a child was murdered in a small town and the lack of suspects was causing large-scale inter-ethnic violence. Some philosophers argue that executing an innocent friend is immoral precisely because it ignores the intrinsic values of justice, friendship, and possibly truth.

Hedonistic Utilitarianism is rarely endorsed by philosophers, but mainly because of its reliance on Prudential Hedonism as opposed to its utilitarian element. Non-hedonistic versions of utilitarianism are about as popular as the other leading theories of right action, especially when it is the actions of institutions that are being considered.

Perhaps the earliest written record of hedonism comes from the Crvka, an Indian philosophical tradition based on the Barhaspatya sutras. The Crvka persisted for two thousand years (from about 600 B.C.E.). Most notably, the Crvka advocated scepticism and Hedonistic Egoism that the right action is the one that brings the actor the most net pleasure. The Crvka acknowledged that some pain often accompanied, or was later caused by, sensual pleasure, but that pleasure was worth it.

The Cyrenaics, founded by Aristippus (c. 435-356 B.C.E.), were also sceptics and Hedonistic Egoists. Although the paucity of original texts makes it difficult to confidently state all of the justifications for the Cyrenaics positions, their overall stance is clear enough. The Cyrenaics believed pleasure was the ultimate good and everyone should pursue all immediate pleasures for themselves. They considered bodily pleasures better than mental pleasures, presumably because they were more vivid or trustworthy. The Cyrenaics also recommended pursuing immediate pleasures and avoiding immediate pains with scant or no regard for future consequences. Their reasoning for this is even less clear, but is most plausibly linked to their sceptical views perhaps that what we can be most sure of in this uncertain existence is our current bodily pleasures.

Epicurus (c. 341-271 B.C.E.), founder of Epicureanism, developed a Normative Hedonism in stark contrast to that of Aristippus. The Epicureanism of Epicurus is also quite the opposite to the common usage of Epicureanism; while we might like to go on a luxurious “Epicurean” holiday packed with fine dining and moderately excessive wining, Epicurus would warn us that we are only setting ourselves up for future pain. For Epicurus, happiness was the complete absence of bodily and especially mental pains, including fear of the Gods and desires for anything other than the bare necessities of life. Even with only the limited excesses of ancient Greece on offer, Epicurus advised his followers to avoid towns, and especially marketplaces, in order to limit the resulting desires for unnecessary things. Once we experience unnecessary pleasures, such as those from sex and rich food, we will then suffer from painful and hard to satisfy desires for more and better of the same. No matter how wealthy we might be, Epicurus would argue, our desires will eventually outstrip our means and interfere with our ability to live tranquil, happy lives. Epicureanism is generally egoistic, in that it encourages everyone to pursue happiness for themselves. However, Epicureans would be unlikely to commit any of the selfish acts we might expect from other egoists because Epicureans train themselves to desire only the very basics, which gives them very little reason to do anything to interfere with the affairs of others.

With the exception of a brief period discussed below, Hedonism has been generally unpopular ever since its ancient beginnings. Although criticisms of the ancient forms of hedonism were many and varied, one in particular was heavily cited. In Philebus, Platos Socrates and one of his many foils, Protarchus in this instance, are discussing the role of pleasure in the good life. Socrates asks Protarchus to imagine a life without much pleasure but full of the higher cognitive processes, such as knowledge, forethought and consciousness and to compare it with a life that is the opposite. Socrates describes this opposite life as having perfect pleasure but the mental life of an oyster, pointing out that the subject of such a life would not be able to appreciate any of the pleasure within it. The harrowing thought of living the pleasurable but unthinking life of an oyster causes Protarchus to abandon his hedonistic argument. The oyster example is now easily avoided by clarifying that pleasure is best understood as being a conscious experience, so any sensation that we are not consciously aware of cannot be pleasure.

Normative and Motivational Hedonism were both at their most popular during the heyday of Empiricism in the 18th and 19th Centuries. Indeed, this is the only period during which any kind of hedonism could be considered popular at all. During this period, two Hedonistic Utilitarians, Jeremy Bentham (1748-1832) and his protg John Stuart Mill (1806-1873), were particularly influential. Their theories are similar in many ways, but are notably distinct on the nature of pleasure.

Bentham argued for several types of hedonism, including those now referred to as Prudential Hedonism, Hedonistic Utilitarianism, and Motivational Hedonism (although his commitment to strong Motivational Hedonism eventually began to wane). Bentham argued that happiness was the ultimate good and that happiness was pleasure and the absence of pain. He acknowledged the egoistic and hedonistic nature of peoples motivation, but argued that the maximization of collective happiness was the correct criterion for moral behavior. Benthams greatest happiness principle states that actions are immoral if they are not the action that appears to maximise the happiness of all the people likely to be affected; only the action that appears to maximise the happiness of all the people likely to be affected is the morally right action.

Bentham devised the greatest happiness principle to justify the legal reforms he also argued for. He understood that he could not conclusively prove that the principle was the correct criterion for morally right action, but also thought that it should be accepted because it was fair and better than existing criteria for evaluating actions and legislation. Bentham thought that his Hedonic Calculus could be applied to situations to see what should, morally speaking, be done in a situation. The Hedonic Calculus is a method of counting the amount of pleasure and pain that would likely be caused by different actions. The Hedonic Calculus required a methodology for measuring pleasure, which in turn required an understanding of the nature of pleasure and specifically what aspects of pleasure were valuable for us.

Benthams Hedonic Calculus identifies several aspects of pleasure that contribute to its value, including certainty, propinquity, extent, intensity, and duration. The Hedonic Calculus also makes use of two future-pleasure-or-pain-related aspects of actions fecundity and purity. Certainty refers to the likelihood that the pleasure or pain will occur. Propinquity refers to how long away (in terms of time) the pleasure or pain is. Fecundity refers to the likelihood of the pleasure or pain leading to more of the same sensation. Purity refers to the likelihood of the pleasure or pain leading to some of the opposite sensation. Extent refers to the number of people the pleasure or pain is likely to affect. Intensity refers to the felt strength of the pleasure or pain. Duration refers to how long the pleasure or pain are felt for. It should be noted that only intensity and duration have intrinsic value for an individual. Certainty, propinquity, fecundity, and purity are all instrumentally valuable for an individual because they affect the likelihood of an individual feeling future pleasure and pain. Extent is not directly valuable for an individuals well-being because it refers to the likelihood of other people experiencing pleasure or pain.

Benthams inclusion of certainty, propinquity, fecundity, and purity in the Hedonic Calculus helps to differentiate his hedonism from Folk Hedonism. Folk Hedonists rarely consider how likely their actions are to lead to future pleasure or pain, focussing instead on the pursuit of immediate pleasure and the avoidance of immediate pain. So while Folk Hedonists would be unlikely to study for an exam, anyone using Benthams Hedonic Calculus would consider the future happiness benefits to themselves (and possibly others) of passing the exam and then promptly begin studying.

Most importantly for Benthams Hedonic Calculus, the pleasure from different sources is always measured against these criteria in the same way, that is to say that no additional value is afforded to pleasures from particularly moral, clean, or culturally-sophisticated sources. For example, Bentham held that pleasure from the parlor game push-pin was just as valuable for us as pleasure from music and poetry. Since Benthams theory of Prudential Hedonism focuses on the quantity of the pleasure, rather than the source-derived quality of it, it is best described as a type of Quantitative Hedonism.

Benthams indifferent stance on the source of pleasures led to others disparaging his hedonism as the philosophy of swine. Even his student, John Stuart Mill, questioned whether we should believe that a satisfied pig leads a better life than a dissatisfied human or that a satisfied fool leads a better life than a dissatisfied Socrates results that Benthams Quantitative Hedonism seems to endorse.

Like Bentham, Mill endorsed the varieties of hedonism now referred to as Prudential Hedonism, Hedonistic Utilitarianism, and Motivational Hedonism. Mill also thought happiness, defined as pleasure and the avoidance of pain, was the highest good. Where Mills hedonism differs from Benthams is in his understanding of the nature of pleasure. Mill argued that pleasures could vary in quality, being either higher or lower pleasures. Mill employed the distinction between higher and lower pleasures in an attempt to avoid the criticism that his hedonism was just another philosophy of swine. Lower pleasures are those associated with the body, which we share with other animals, such as pleasure from quenching thirst or having sex. Higher pleasures are those associated with the mind, which were thought to be unique to humans, such as pleasure from listening to opera, acting virtuously, and philosophising. Mill justified this distinction by arguing that those who have experienced both types of pleasure realise that higher pleasures are much more valuable. He dismissed challenges to this claim by asserting that those who disagreed lacked either the experience of higher pleasures or the capacity for such experiences. For Mill, higher pleasures were not different from lower pleasures by mere degree; they were different in kind. Since Mills theory of Prudential Hedonism focuses on the quality of the pleasure, rather than the amount of it, it is best described as a type of Qualitative Hedonism.

George Edward Moore (1873-1958) was instrumental in bringing hedonisms brief heyday to an end. Moores criticisms of hedonism in general, and Mills hedonism in particular, were frequently cited as good reasons to reject hedonism even decades after his death. Indeed, since G. E. Moore, hedonism has been viewed by most philosophers as being an initially intuitive and interesting family of theories, but also one that is flawed on closer inspection. Moore was a pluralist about value and argued persuasively against the Value Hedonists central claim that all and only pleasure is the bearer of intrinsic value. Moores most damaging objection against Hedonism was his heap of filth example. Moore himself thought the heap of filth example thoroughly refuted what he saw as the only potentially viable form of Prudential Hedonism that conscious pleasure is the only thing that positively contributes to well-being. Moore used the heap of filth example to argue that Prudential Hedonism is false because pleasure is not the only thing of value.

In the heap of filth example, Moore asks the reader to imagine two worlds, one of which is exceedingly beautiful and the other a disgusting heap of filth. Moore then instructs the reader to imagine that no one would ever experience either world and asks if it is better for the beautiful world to exist than the filthy one. As Moore expected, his contemporaries tended to agree that it would be better if the beautiful world existed. Relying on this agreement, Moore infers that the beautiful world is more valuable than the heap of filth and, therefore, that beauty must be valuable. Moore then concluded that all of the potentially viable theories of Prudential Hedonism (those that value only conscious pleasures) must be false because something, namely beauty, is valuable even when no conscious pleasure can be derived from it.

Moores heap of filth example has rarely been used to object to Prudential Hedonism since the 1970s because it is not directly relevant to Prudential Hedonism (it evaluates worlds and not lives). Moores other objections to Prudential Hedonism also went out of favor around the same time. The demise of these arguments was partly due to mounting objections against them, but mainly because arguments more suited to the task of refuting Prudential Hedonism were developed. These arguments are discussed after the contemporary varieties of hedonism are introduced below.

Several contemporary varieties of hedonism have been defended, although usually by just a handful of philosophers or less at any one time. Other varieties of hedonism are also theoretically available but have received little or no discussion. Contemporary varieties of Prudential Hedonism can be grouped based on how they define pleasure and pain, as is done below. In addition to providing different notions of what pleasure and pain are, contemporary varieties of Prudential Hedonism also disagree about what aspect or aspects of pleasure are valuable for well-being (and the opposite for pain).

The most well-known disagreement about what aspects of pleasure are valuable occurs between Quantitative and Qualitative Hedonists. Quantitative Hedonists argue that how valuable pleasure is for well-being depends on only the amount of pleasure, and so they are only concerned with dimensions of pleasure such as duration and intensity. Quantitative Hedonism is often accused of over-valuing animalistic, simple, and debauched pleasures.

Qualitative Hedonists argue that, in addition to the dimensions related to the amount of pleasure, one or more dimensions of quality can have an impact on how pleasure affects well-being. The quality dimensions might be based on how cognitive or bodily the pleasure is (as it was for Mill), the moral status of the source of the pleasure, or some other non-amount-related dimension. Qualitative Hedonism is criticised by some for smuggling values other than pleasure into well-being by misleadingly labelling them as dimensions of pleasure. How these qualities are chosen for inclusion is also criticised for being arbitrary or ad hoc by some because inclusion of these dimensions of pleasure is often in direct response to objections that Quantitative Hedonism cannot easily deal with. That is to say, the inclusion of these dimensions is often accused of being an exercise in plastering over holes, rather than deducing corollary conclusions from existing theoretical premises. Others have argued that any dimensions of quality can be better explained in terms of dimensions of quantity. For example, they might claim that moral pleasures are no higher in quality than immoral pleasures, but that moral pleasures are instrumentally more valuable because they are likely to lead to more moments of pleasure or less moments of pain in the future.

Hedonists also have differing views about how the value of pleasure compares with the value of pain. This is not a practical disagreement about how best to measure pleasure and pain, but rather a theoretical disagreement about comparative value, such as whether pain is worse for us than an equivalent amount of pleasure is good for us. The default position is that one unit of pleasure (sometimes referred to as a Hedon) is equivalent but opposite in value to one unit of pain (sometimes referred to as a Dolor). Several Hedonistic Utilitarians have argued that reduction of pain should be seen as more important than increasing pleasure, sometimes for the Epicurean reason that pain seems worse for us than an equivalent amount of pleasure is good for us. Imagine that a magical genie offered for you to play a game with him. The game consists of you flipping a fair coin. If the coin lands on heads, then you immediately feel a burst of very intense pleasure and if it lands on tails, then you immediately feel a burst of very intense pain. Is it in your best interests to play the game?

Another area of disagreement between some Hedonists is whether pleasure is entirely internal to a person or if it includes external elements. Internalism about pleasure is the thesis that, whatever pleasure is, it is always and only inside a person. Externalism about pleasure, on the other hand, is the thesis that, pleasure is more than just a state of an individual (that is, that a necessary component of pleasure lies outside of the individual). Externalists about pleasure might, for example, describe pleasure as a function that mediates between our minds and the environment, such that every instance of pleasure has one or more integral environmental components. The vast majority of historic and contemporary versions of Prudential Hedonism consider pleasure to be an internal mental state.

Perhaps the least known disagreement about what aspects of pleasure make it valuable is the debate about whether we have to be conscious of pleasure for it to be valuable. The standard position is that pleasure is a conscious mental state, or at least that any pleasure a person is not conscious of does not intrinsically improve their well-being.

The most common definition of pleasure is that it is a sensation, something that we identify through our senses or that we feel. Psychologists claim that we have at least ten senses, including the familiar, sight, hearing, smell, taste, and touch, but also, movement, balance, and several sub-senses of touch, including heat, cold, pressure, and pain. New senses get added to the list when it is understood that some independent physical process underpins their functioning. The most widely-used examples of pleasurable sensations are the pleasures of eating, drinking, listening to music, and having sex. Use of these examples has done little to help Hedonism avoid its debauched reputation.

It is also commonly recognised that our senses are physical processes that usually involve a mental component, such as the tickling feeling when someone blows gently on the back of your neck. If a sensation is something we identify through our sense organs, however, it is not entirely clear how to account for abstract pleasures. This is because abstract pleasures, such as a feeling of accomplishment for a job well done, do not seem to be experienced through any of the senses in the standard lists. Some Hedonists have attempted to resolve this problem by arguing for the existence of an independent pleasure sense and by defining sensation as something that we feel (regardless of whether it has been mediated by sense organs).

Most Hedonists who describe pleasure as a sensation will be Quantitative Hedonists and will argue that the pleasure from the different senses is the same. Qualitative Hedonists, in comparison, can use the framework of the senses to help differentiate between qualities of pleasure. For example, a Qualitative Hedonist might argue that pleasurable sensations from touch and movement are always lower quality than the others.

Hedonists have also defined pleasure as intrinsically valuable experience, that is to say any experiences that we find intrinsically valuable either are, or include, instances of pleasure. According to this definition, the reason that listening to music and eating a fine meal are both intrinsically pleasurable is because those experiences include an element of pleasure (along with the other elements specific to each activity, such as the experience of the texture of the food and the melody of the music). By itself, this definition enables Hedonists to make an argument that is close to perfectly circular. Defining pleasure as intrinsically valuable experience and well-being as all and only experiences that are intrinsically valuable allows a Hedonist to all but stipulate that Prudential Hedonism is the correct theory of well-being. Where defining pleasure as intrinsically valuable experience is not circular is in its stipulation that only experiences matter for well-being. Some well-known objections to this idea are discussed below.

Another problem with defining pleasure as intrinsically valuable experience is that the definition does not tell us very much about what pleasure is or how it can be identified. For example, knowing that pleasure is intrinsically valuable experience would not help someone to work out if a particular experience was intrinsically or just instrumentally valuable. Hedonists have attempted to respond to this problem by explaining how to find out whether an experience is intrinsically valuable.

One method is to ask yourself if you would like the experience to continue for its own sake (rather than because of what it might lead to). Wanting an experience to continue for its own sake reveals that you find it to be intrinsically valuable. While still making a coherent theory of well-being, defining intrinsically valuable experiences as those you want to perpetuate makes the theory much less hedonistic. The fact that what a person wants is the main criterion for something having intrinsic value, makes this kind of theory more in line with preference satisfaction theories of well-being. The central claim of preference satisfaction theories of well-being is that some variant of getting what one wants, or should want, under certain conditions is the only thing that intrinsically improves ones well-being.

Another method of fleshing out the definition of pleasure as intrinsically valuable experience is to describe how intrinsically valuable experiences feel. This method remains a hedonistic one, but seems to fall back into defining pleasure as a sensation.

It has also been argued that what makes an experience intrinsically valuable is that you like or enjoy it for its own sake. Hedonists arguing for this definition of pleasure usually take pains to position their definition in between the realms of sensation and preference satisfaction. They argue that since we can like or enjoy some experiences without concurrently wanting them or feeling any particular sensation, then liking is distinct from both sensation and preference satisfaction. Liking and enjoyment are also difficult terms to define in more detail, but they are certainly easier to recognise than the rather opaque “intrinsically valuable experience.”

Merely defining pleasure as intrinsically valuable experience and intrinsically valuable experiences as those that we like or enjoy still lacks enough detail to be very useful for contemplating well-being. A potential method for making this theory more useful would be to draw on the cognitive sciences to investigate if there is a specific neurological function for liking or enjoying. Cognitive science has not reached the point where anything definitive can be said about this, but a few neuroscientists have experimental evidence that liking and wanting (at least in regards to food) are neurologically distinct processes in rats and have argued that it should be the same for humans. The same scientists have wondered if the same processes govern all of our liking and wanting, but this question remains unresolved.

Most Hedonists who describe pleasure as intrinsically valuable experience believe that pleasure is internal and conscious. Hedonists who define pleasure in this way may be either Quantitative or Qualitative Hedonists, depending on whether they think that quality is a relevant dimension of how intrinsically valuable we find certain experiences.

One of the most recent developments in modern hedonism is the rise of defining pleasure as a pro-attitude a positive psychological stance toward some object. Any account of Prudential Hedonism that defines pleasure as a pro-attitude is referred to as Attitudinal Hedonism because it is a persons attitude that dictates whether anything has intrinsic value. Positive psychological stances include approving of something, thinking it is good, and being pleased about it. The object of the positive psychological stance could be a physical object, such as a painting one is observing, but it could also be a thought, such as “my country is not at war,” or even a sensation. An example of a pro-attitude towards a sensation could be being pleased about the fact that an ice cream tastes so delicious.

Fred Feldman, the leading proponent of Attitudinal Hedonism, argues that the sensation of pleasure only has instrumental value it only brings about value if you also have a positive psychological stance toward that sensation. In addition to his basic Intrinsic Attitudinal Hedonism, which is a form of Quantitative Hedonism, Feldman has also developed many variants that are types of Qualitative Hedonism. For example, Desert-Adjusted Intrinsic Attitudinal Hedonism, which reduces the intrinsic value a pro-attitude has for our well-being based on the quality of deservedness (that is, on the extent to which the particular object deserves a pro-attitude or not). For example, Desert-Adjusted Intrinsic Attitudinal Hedonism might stipulate that sensations of pleasure arising from adulterous behavior do not deserve approval, and so assign them no value.

Defining pleasure as a pro-attitude, while maintaining that all sensations of pleasure have no intrinsic value, makes Attitudinal Hedonism less obviously hedonistic as the versions that define pleasure as a sensation. Indeed, defining pleasure as a pro-attitude runs the risk of creating a preference satisfaction account of well-being because being pleased about something without feeling any pleasure seems hard to distinguish from having a preference for that thing.

The most common argument against Prudential Hedonism is that pleasure is not the only thing that intrinsically contributes to well-being. Living in reality, finding meaning in life, producing noteworthy achievements, building and maintaining friendships, achieving perfection in certain domains, and living in accordance with religious or moral laws are just some of the other things thought to intrinsically add value to our lives. When presented with these apparently valuable aspects of life, Hedonists usually attempt to explain their apparent value in terms of pleasure. A Hedonist would argue, for example, that friendship is not valuable in and of itself, rather it is valuable to the extent that it brings us pleasure. Furthermore, to answer why we might help a friend even when it harms us, a Hedonist will argue that the prospect of future pleasure from receiving reciprocal favors from our friend, rather than the value of friendship itself, should motivate us to help in this way.

Those who object to Prudential Hedonism on the grounds that pleasure is not the only source of intrinsic value use two main strategies. In the first strategy, objectors make arguments that some specific value cannot be reduced to pleasure. In the second strategy, objectors cite very long lists of apparently intrinsically valuable aspects of life and then challenge hedonists with the prolonged and arduous task of trying to explain how the value of all of them can be explained solely by reference to pleasure and the avoidance of pain. This second strategy gives good reason to be a pluralist about value because the odds seem to be against any monistic theory of value, such as Prudential Hedonism. The first strategy, however, has the ability to show that Prudential Hedonism is false, rather than being just unlikely to be the best theory of well-being.

The most widely cited argument for pleasure not being the only source of intrinsic value is based on Robert Nozicks experience machine thought-experiment. Nozicks experience machine thought-experiment was designed to show that more than just our experiences matter to us because living in reality also matters to us. This argument has proven to be so convincing that nearly every single book on ethics that discusses hedonism rejects it using only this argument or this one and one other.

In the thought experiment, Nozick asks us to imagine that we have the choice of plugging in to a fantastic machine that flawlessly provides an amazing mix of experiences. Importantly, this machine can provide these experiences in a way that, once plugged in to the machine, no one can tell that their experiences are not real. Disregarding considerations about responsibilities to others and the problems that would arise if everyone plugged in, would you plug in to the machine for life? The vast majority of people reject the choice to live a much more pleasurable life in the machine, mostly because they agree with Nozick that living in reality seems to be important for our well-being. Opinions differ on what exactly about living in reality is so much better for us than the additional pleasure of living in the experience machine, but the most common response is that a life that is not lived in reality is pointless or meaningless.

Since this argument has been used so extensively (from the mid 1970s onwards) to dismiss Prudential Hedonism, several attempts have been made to refute it. Most commonly, Hedonists argue that living an experience machine life would be better than living a real life and that most people are simply mistaken to not want to plug in. Some go further and try to explain why so many people choose not to plug in. Such explanations often point out that the most obvious reasons for not wanting to plug in can be explained in terms of expected pleasure and avoidance of pain. For example, it might be argued that we expect to get pleasure from spending time with our real friends and family, but we do not expect to get as much pleasure from the fake friends or family we might have in the experience machine. These kinds of attempts to refute the experience machine objection do little to persuade non-Hedonists that they have made the wrong choice.

A more promising line of defence for the Prudential Hedonists is to provide evidence that there is a particular psychological bias that affects most peoples choice in the experience machine thought experiment. A reversal of Nozicks thought experiment has been argued to reveal just such a bias. Imagine that a credible source tells you that you are actually in an experience machine right now. You have no idea what reality would be like. Given the choice between having your memory of this conversation wiped and going to reality, what would be best for you to choose? Empirical evidence on this choice shows that most people would choose to stay in the experience machine. Comparing this result with how people respond to Nozicks experience machine thought experiment reveals the following: In Nozicks experience machine thought experiment people tend to choose a real and familiar life over a more pleasurable life and in the reversed experience machine thought experiment people tend to choose a familiar life over a real life. Familiarity seems to matter more than reality, undermining the strength of Nozicks original argument. The bias thought to be responsible for this difference is the status quo bias an irrational preference for the familiar or for things to stay as they are.

Regardless of whether Nozicks experience machine thought experiment is as decisive a refutation of Prudential Hedonism as it is often thought to be, the wider argument (that living in reality is valuable for our well-being) is still a problem for Prudential Hedonists. That our actions have real consequences, that our friends are real, and that our experiences are genuine seem to matter for most of us regardless of considerations of pleasure. Unfortunately, we lack a trusted methodology for discerning if these things should matter to us. Perhaps the best method for identifying intrinsically valuable aspects of lives is to compare lives that are equal in pleasure and all other important ways, except that one aspect of one of the lives is increased. Using this methodology, however, seems certain to lead to an artificial pluralist conclusion about what has value. This is because any increase in a potentially valuable aspect of our lives will be viewed as a free bonus. And, most people will choose the life with the free bonus just in case it has intrinsic value, not necessarily because they think it does have intrinsic value.

The main traditional line of criticism against Prudential Hedonism is that not all pleasure is valuable for well-being, or at least that some pleasures are less valuable than others because of non-amount-related factors. Some versions of this criticism are much easier for Prudential Hedonists to deal with than others depending on where the allegedly disvaluable aspect of the pleasure resides. If the disvaluable aspect is experienced with the pleasure itself, then both Qualitative and Quantitative varieties of Prudential Hedonism have sufficient answers to these problems. If, however, the disvaluable aspect of the pleasure is never experienced, then all types of Prudential Hedonism struggle to explain why the allegedly disvaluable aspect is irrelevant.

Examples of the easier criticisms to deal with are that Prudential Hedonism values, or at least overvalues, perverse and base pleasures. These kinds of criticisms tend to have had more sway in the past and doubtless encouraged Mill to develop his Qualitative Hedonism. In response to the charge that Prudential Hedonism mistakenly values pleasure from sadistic torture, sating hunger, copulating, listening to opera, and philosophising all equally, Qualitative Hedonists can simply deny that it does. Since pleasure from sadistic torture will normally be experienced as containing the quality of sadism (just as the pleasure from listening to good opera is experienced as containing the quality of acoustic excellence), the Qualitative Hedonist can plausibly claim to be aware of the difference in quality and allocate less value to perverse or base pleasures accordingly.

Prudential Hedonists need not relinquish the Quantitative aspect of their theory in order to deal with these criticisms, however. Quantitative Hedonists, can simply point out that moral or cultural values are not necessarily relevant to well-being because the investigation of well-being aims to understand what the good life for the one living it is and what intrinsically makes their life go better for them. A Quantitative Hedonist can simply respond that a sadist that gets sadistic pleasure from torturing someone does improve their own well-being (assuming that the sadist never feels any negative emotions or gets into any other trouble as a result). Similarly, a Quantitative Hedonist can argue that if someone genuinely gets a lot of pleasure from porcine company and wallowing in the mud, but finds opera thoroughly dull, then we have good reason to think that having to live in a pig sty would be better for her well-being than forcing her to listen to opera.

Much more problematic for both Quantitative and Qualitative Hedonists, however, are the more modern versions of the criticism that not all pleasure is valuable. The modern versions of this criticism tend to use examples in which the disvaluable aspect of the pleasure is never experienced by the person whose well-being is being evaluated. The best example of these modern criticisms is a thought experiment devised by Shelly Kagan. Kagans deceived businessman thought experiment is widely thought to show that pleasures of a certain kind, namely false pleasures, are worth much less than true pleasures.

Kagan asks us to imagine the life of a very successful businessman who takes great pleasure in being respected by his colleagues, well-liked by his friends, and loved by his wife and children until the day he died. Then Kagan asks us to compare this life with one of equal length and the same amount of pleasure (experienced as coming from exactly the same sources), except that in each case the businessman is mistaken about how those around him really feel. This second (deceived) businessman experiences just as much pleasure from the respect of his colleagues and the love of his family as the first businessman. The only difference is that the second businessman has many false beliefs. Specifically, the deceived businessmans colleagues actually think he is useless, his wife doesnt really love him, and his children are only nice to him so that he will keep giving them money. Given that the deceived businessman never knew of any of these deceptions and his experiences were never negatively impacted by the deceptions indirectly, which life do you think is better?

Nearly everyone thinks that the deceived businessman has a worse life. This is a problem for Prudential Hedonists because the pleasure is quantitatively equal in each life, so they should be equally good for the one living it. Qualitative Hedonism does not seem to be able to avoid this criticism either because the falsity of the pleasures experienced by the deceived businessman is a dimension of the pleasure that he never becomes aware of. Theoretically, an externalist and qualitative version of Attitudinal Hedonism could include the falsity dimension of an instance of pleasure even if the falsity dimension never impacts the consciousness of the person. However, the resulting definition of pleasure bears little resemblance to what we commonly understand pleasure to be and also seems to be ad hoc in its inclusion of the truth dimension but not others. A dedicated Prudential Hedonist of any variety can always stubbornly stick to the claim that the lives of the two businessmen are of equal value, but that will do little to convince the vast majority to take Prudential Hedonism more seriously.

Another major line of criticism used against Prudential Hedonists is that they have yet to come up with a meaningful definition of pleasure that unifies the seemingly disparate array of pleasures while remaining recognisable as pleasure. Some definitions lack sufficient detail to be informative about what pleasure actually is, or why it is valuable, and those that do offer enough detail to be meaningful are faced with two difficult tasks.

The first obstacle for a useful definition of pleasure for hedonism is to unify all of the diverse pleasures in a reasonable way. Phenomenologically, the pleasure from reading a good book is very different to the pleasure from bungee jumping, and both of these pleasures are very different to the pleasure of having sex. This obstacle is unsurpassable for most versions of Quantitative Hedonism because it makes the value gained from different pleasures impossible to compare. Not being able to compare different types of pleasure results in being unable to say if a life is better than another in most even vaguely realistic cases. Furthermore, not being able to compare lives means that Quantitative Hedonism could not be usefully used to guide behavior since it cannot instruct us on which life to aim for.

Attempts to resolve the problem of unifying the different pleasures while remaining within a framework of Quantitative Hedonism, usually involve pointing out something that is constant in all of the disparate pleasures and defining that particular thing as pleasure. When pleasure is defined as a strict sensation, this strategy fails because introspection reveals that no such sensation exists. Pleasure defined as the experience of liking or as a pro-attitude does much better at unifying all of the diverse pleasures. However, defining pleasure in these ways makes the task of filling in the details of the theory a fine balancing act. Liking or pro-attitudes must be described in such a way that they are not solely a sensation or best described as a preference satisfaction theory. And they must perform this balancing act while still describing a scientifically plausible and conceptually coherent account of pleasure. Most attempts to define pleasure as liking or pro-attitudes seem to disagree with either the folk conception of what pleasure is or any of the plausible scientific conceptions of how pleasure functions.

Most varieties of Qualitative Hedonism do better at dealing with the problem of diverse pleasures because they can evaluate different pleasures according to their distinct qualities. Qualitative Hedonists still need a coherent method for comparing the different pleasures with each other in order to be more than just an abstract theory of well-being, however. And, it is difficult to construct such a methodology in a way that avoids counter examples, while still describing a scientifically plausible and conceptually coherent account of pleasure.

The second obstacle is creating a definition of pleasure that retains at least some of the core properties of the common understanding of the term pleasure. As mentioned, many of the potential adjustments to the main definitions of pleasure are useful for avoiding one or more of the many objections against Prudential Hedonism. The problem with this strategy is that the more adjustments that are made, the more apparent it becomes that the definition of pleasure is not recognisable as the pleasure that gave Hedonism its distinctive intuitive plausibility in the first place. When an instance of pleasure is defined simply as when someone feels good, its intrinsic value for well-being is intuitively obvious. However, when the definition of pleasure is stretched, so as to more effectively argue that all valuable experiences are pleasurable, it becomes much less recognisable as the concept of pleasure we use in day-to-day life and its intrinsic value becomes much less intuitive.

The future of hedonism seems bleak. The considerable number and strength of the arguments against Prudential Hedonisms central principle (that pleasure and only pleasure intrinsically contributes positively to well-being and the opposite for pain) seem insurmountable. Hedonists have been creative in their definitions of pleasure so as to avoid these objections, but more often than not find themselves defending a theory that is not particularly hedonistic, realistic or both.

Perhaps the only hope that Hedonists of all types can have for the future is that advances in cognitive science will lead to a better understanding of how pleasure works in the brain and how biases affect our judgements about thought experiments. If our improved understanding in these areas confirms a particular theory about what pleasure is and also provides reasons to doubt some of the widespread judgements about the thought experiments that make the vast majority of philosophers reject hedonism, then hedonism might experience at least a partial revival. The good news for Hedonists is that at least some emerging theories and results from cognitive science do appear to support some aspects of hedonism.

Dan WeijersEmail: danweijers@gmail.comVictoria University of WellingtonNew Zealand

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Hedonism | Internet Encyclopedia of Philosophy

Hedonism – Wikipedia

Hedonism is a school of thought that argues that pleasure and happiness are the primary or most important intrinsic goods and the aim of human life.[1] A hedonist strives to maximize net pleasure (pleasure minus pain), but when having finally gained that pleasure, happiness remains stationary.

Ethical hedonism is the idea that all people have the right to do everything in their power to achieve the greatest amount of pleasure possible to them. It is also the idea that every person’s pleasure should far surpass their amount of pain. Ethical hedonism is said to have been started by Aristippus of Cyrene, a student of Socrates. He held the idea that pleasure is the highest good.[2]

The name derives from the Greek word for “delight” ( hdonismos from hdon “pleasure”, cognate[according to whom?] with English sweet + suffix – -ismos “ism”). An extremely strong aversion to hedonism is hedonophobia.

In the original Old Babylonian version of the Epic of Gilgamesh, which was written soon after the invention of writing, Siduri gave the following advice “Fill your belly. Day and night make merry. Let days be full of joy. Dance and make music day and night […] These things alone are the concern of men”, which may represent the first recorded advocacy of a hedonistic philosophy.[3]

Scenes of a harper entertaining guests at a feast were common in ancient Egyptian tombs (see Harper’s Songs), and sometimes contained hedonistic elements, calling guests to submit to pleasure because they cannot be sure that they will be rewarded for good with a blissful afterlife. The following is a song attributed to the reign of one of the pharaohs around the time of the 12th dynasty, and the text was used in the eighteenth and nineteenth dynasties.[4][5]

Let thy desire flourish,In order to let thy heart forget the beatifications for thee.Follow thy desire, as long as thou shalt live.Put myrrh upon thy head and clothing of fine linen upon thee,Being anointed with genuine marvels of the gods’ property.Set an increase to thy good things;Let not thy heart flag.Follow thy desire and thy good.Fulfill thy needs upon earth, after the command of thy heart,Until there come for thee that day of mourning.

Democritus seems to be the earliest philosopher on record to have categorically embraced a hedonistic philosophy; he called the supreme goal of life “contentment” or “cheerfulness”, claiming that “joy and sorrow are the distinguishing mark of things beneficial and harmful” (DK 68 B 188).[6]

The Cyrenaics were an ultra-hedonist Greek school of philosophy founded in the 4th century BC, supposedly by Aristippus of Cyrene, although many of the principles of the school are believed to have been formalized by his grandson of the same name, Aristippus the Younger. The school was so called after Cyrene, the birthplace of Aristippus. It was one of the earliest Socratic schools. The Cyrenaics taught that the only intrinsic good is pleasure, which meant not just the absence of pain, but positively enjoyable sensations. Of these, momentary pleasures, especially physical ones, are stronger than those of anticipation or memory. They did, however, recognize the value of social obligation, and that pleasure could be gained from altruism[citation needed]. Theodorus the Atheist was a latter exponent of hedonism who was a disciple of younger Aristippus,[7] while becoming well known for expounding atheism. The school died out within a century, and was replaced by Epicureanism.

The Cyrenaics were known for their skeptical theory of knowledge. They reduced logic to a basic doctrine concerning the criterion of truth.[8] They thought that we can know with certainty our immediate sense-experiences (for instance, that I am having a sweet sensation now) but can know nothing about the nature of the objects that cause these sensations (for instance, that the honey is sweet).[9] They also denied that we can have knowledge of what the experiences of other people are like.[10] All knowledge is immediate sensation. These sensations are motions which are purely subjective, and are painful, indifferent or pleasant, according as they are violent, tranquil or gentle.[9][11] Further they are entirely individual, and can in no way be described as constituting absolute objective knowledge. Feeling, therefore, is the only possible criterion of knowledge and of conduct.[9] Our ways of being affected are alone knowable. Thus the sole aim for everyone should be pleasure.

Cyrenaicism deduces a single, universal aim for all people which is pleasure. Furthermore, all feeling is momentary and homogeneous. It follows that past and future pleasure have no real existence for us, and that among present pleasures there is no distinction of kind.[11] Socrates had spoken of the higher pleasures of the intellect; the Cyrenaics denied the validity of this distinction and said that bodily pleasures, being more simple and more intense, were preferable.[12] Momentary pleasure, preferably of a physical kind, is the only good for humans. However some actions which give immediate pleasure can create more than their equivalent of pain. The wise person should be in control of pleasures rather than be enslaved to them, otherwise pain will result, and this requires judgement to evaluate the different pleasures of life.[13] Regard should be paid to law and custom, because even though these things have no intrinsic value on their own, violating them will lead to unpleasant penalties being imposed by others.[12] Likewise, friendship and justice are useful because of the pleasure they provide.[12] Thus the Cyrenaics believed in the hedonistic value of social obligation and altruistic behaviour.

Epicureanism is a system of philosophy based upon the teachings of Epicurus (c. 341c. 270 BC), founded around 307 BC. Epicurus was an atomic materialist, following in the steps of Democritus and Leucippus. His materialism led him to a general stance against superstition or the idea of divine intervention. Following Aristippusabout whom very little is knownEpicurus believed that the greatest good was to seek modest, sustainable “pleasure” in the form of a state of tranquility and freedom from fear (ataraxia) and absence of bodily pain (aponia) through knowledge of the workings of the world and the limits of our desires. The combination of these two states is supposed to constitute happiness in its highest form. Although Epicureanism is a form of hedonism, insofar as it declares pleasure as the sole intrinsic good, its conception of absence of pain as the greatest pleasure and its advocacy of a simple life make it different from “hedonism” as it is commonly understood.

In the Epicurean view, the highest pleasure (tranquility and freedom from fear) was obtained by knowledge, friendship and living a virtuous and temperate life. He lauded the enjoyment of simple pleasures, by which he meant abstaining from bodily desires, such as sex and appetites, verging on asceticism. He argued that when eating, one should not eat too richly, for it could lead to dissatisfaction later, such as the grim realization that one could not afford such delicacies in the future. Likewise, sex could lead to increased lust and dissatisfaction with the sexual partner. Epicurus did not articulate a broad system of social ethics that has survived but had a unique version of the Golden Rule.

It is impossible to live a pleasant life without living wisely and well and justly (agreeing “neither to harm nor be harmed”),[14] and it is impossible to live wisely and well and justly without living a pleasant life.[15]

Epicureanism was originally a challenge to Platonism, though later it became the main opponent of Stoicism. Epicurus and his followers shunned politics. After the death of Epicurus, his school was headed by Hermarchus; later many Epicurean societies flourished in the Late Hellenistic era and during the Roman era (such as those in Antiochia, Alexandria, Rhodes and Ercolano). The poet Lucretius is its most known Roman proponent. By the end of the Roman Empire, having undergone Christian attack and repression, Epicureanism had all but died out, and would be resurrected in the 17th century by the atomist Pierre Gassendi, who adapted it to the Christian doctrine.

Some writings by Epicurus have survived. Some scholars consider the epic poem On the Nature of Things by Lucretius to present in one unified work the core arguments and theories of Epicureanism. Many of the papyrus scrolls unearthed at the Villa of the Papyri at Herculaneum are Epicurean texts. At least some are thought to have belonged to the Epicurean Philodemus.

Yangism has been described as a form of psychological and ethical egoism. The Yangist philosophers believed in the importance of maintaining self-interest through “keeping one’s nature intact, protecting one’s uniqueness, and not letting the body be tied by other things.” Disagreeing with the Confucian virtues of li (propriety), ren (humaneness), and yi (righteousness) and the Legalist virtue of fa (law), the Yangists saw wei wo, or “everything for myself,” as the only virtue necessary for self-cultivation. Individual pleasure is considered desirable, like in hedonism, but not at the expense of the health of the individual. The Yangists saw individual well-being as the prime purpose of life, and considered anything that hindered that well-being immoral and unnecessary.

The main focus of the Yangists was on the concept of xing, or human nature, a term later incorporated by Mencius into Confucianism. The xing, according to sinologist A. C. Graham, is a person’s “proper course of development” in life. Individuals can only rationally care for their own xing, and should not naively have to support the xing of other people, even if it means opposing the emperor. In this sense, Yangism is a “direct attack” on Confucianism, by implying that the power of the emperor, defended in Confucianism, is baseless and destructive, and that state intervention is morally flawed.

The Confucian philosopher Mencius depicts Yangism as the direct opposite of Mohism, while Mohism promotes the idea of universal love and impartial caring, the Yangists acted only “for themselves,” rejecting the altruism of Mohism. He criticized the Yangists as selfish, ignoring the duty of serving the public and caring only for personal concerns. Mencius saw Confucianism as the “Middle Way” between Mohism and Yangism.

Judaism believes that mankind was created for pleasure, as God placed Adam and Eve in the Garden of EdenEden being the Hebrew word for “pleasure.” In recent years, Rabbi Noah Weinberg articulated five different levels of pleasure; connecting with God is the highest possible pleasure.

Christian doctrine current in some evangelical circles, particularly those of the Reformed tradition.[16] The term was first coined by Reformed Baptist theologian John Piper in his 1986 book Desiring God: My shortest summary of it is: God is most glorified in us when we are most satisfied in him. Or: The chief end of man is to glorify God by enjoying him forever. Does Christian Hedonism make a god out of pleasure? No. It says that we all make a god out of what we take most pleasure in. [16] Piper states his term may describe the theology of Jonathan Edwards, who referred to a future enjoyment of him [God] in heaven.[17] In the 17th century, the atomist Pierre Gassendi adapted Epicureanism to the Christian doctrine.

The concept of hedonism is also found in the Hindu scriptures.[18][19]

Utilitarianism addresses problems with moral motivation neglected by Kantianism by giving a central role to happiness. It is an ethical theory holding that the proper course of action is the one that maximizes the overall good of the society.[20] It is thus one form of consequentialism, meaning that the moral worth of an action is determined by its resulting outcome. The most influential contributors to this theory are considered to be the 18th and 19th-century British philosophers Jeremy Bentham and John Stuart Mill. Conjoining hedonismas a view as to what is good for peopleto utilitarianism has the result that all action should be directed toward achieving the greatest total amount of happiness (see Hedonic calculus). Though consistent in their pursuit of happiness, Bentham and Mill’s versions of hedonism differ. There are two somewhat basic schools of thought on hedonism:[1]

Contemporary proponents of hedonism include Swedish philosopher Torbjrn Tnnsj,[21] Fred Feldman.[22] and Spanish ethic philosopher Esperanza Guisn (published a “Hedonist manifesto” in 1990).[23]

A dedicated contemporary hedonist philosopher and writer on the history of hedonistic thought is the French Michel Onfray. He has written two books directly on the subject (L’invention du plaisir: fragments cyraniques[24] and La puissance d’exister: Manifeste hdoniste).[25] He defines hedonism “as an introspective attitude to life based on taking pleasure yourself and pleasuring others, without harming yourself or anyone else.”[26] Onfray’s philosophical project is to define an ethical hedonism, a joyous utilitarianism, and a generalized aesthetic of sensual materialism that explores how to use the brain’s and the body’s capacities to their fullest extent — while restoring philosophy to a useful role in art, politics, and everyday life and decisions.”[27]

Onfray’s works “have explored the philosophical resonances and components of (and challenges to) science, painting, gastronomy, sex and sensuality, bioethics, wine, and writing. His most ambitious project is his projected six-volume Counter-history of Philosophy,”[27] of which three have been published. For him “In opposition to the ascetic ideal advocated by the dominant school of thought, hedonism suggests identifying the highest good with your own pleasure and that of others; the one must never be indulged at the expense of sacrificing the other. Obtaining this balance my pleasure at the same time as the pleasure of others presumes that we approach the subject from different angles political, ethical, aesthetic, erotic, bioethical, pedagogical, historiographical.”

For this he has “written books on each of these facets of the same world view.”[28] His philosophy aims for “micro-revolutions”, or “revolutions of the individual and small groups of like-minded people who live by his hedonistic, libertarian values.”[29]

The Abolitionist Society is a transhumanist group calling for the abolition of suffering in all sentient life through the use of advanced biotechnology. Their core philosophy is negative utilitarianism. David Pearce is a theorist of this perspective and he believes and promotes the idea that there exists a strong ethical imperative for humans to work towards the abolition of suffering in all sentient life. His book-length internet manifesto The Hedonistic Imperative[30] outlines how technologies such as genetic engineering, nanotechnology, pharmacology, and neurosurgery could potentially converge to eliminate all forms of unpleasant experience among human and non-human animals, replacing suffering with gradients of well-being, a project he refers to as “paradise engineering”.[31] A transhumanist and a vegan,[32] Pearce believes that we (or our future posthuman descendants) have a responsibility not only to avoid cruelty to animals within human society but also to alleviate the suffering of animals in the wild.

In a talk David Pearce gave at the Future of Humanity Institute and at the Charity International ‘Happiness Conference’ he said “Sadly, what won’t abolish suffering, or at least not on its own, is socio-economic reform, or exponential economic growth, or technological progress in the usual sense, or any of the traditional panaceas for solving the world’s ills. Improving the external environment is admirable and important; but such improvement can’t recalibrate our hedonic treadmill above a genetically constrained ceiling. Twin studies confirm there is a [partially] heritable set-point of well-being – or ill-being – around which we all tend to fluctuate over the course of a lifetime. This set-point varies between individuals. [It’s possible to lower an individual’s hedonic set-point by inflicting prolonged uncontrolled stress; but even this re-set is not as easy as it sounds: suicide-rates typically go down in wartime; and six months after a quadriplegia-inducing accident, studies[citation needed] suggest that we are typically neither more nor less unhappy than we were before the catastrophic event.] Unfortunately, attempts to build an ideal society can’t overcome this biological ceiling, whether utopias of the left or right, free-market or socialist, religious or secular, futuristic high-tech or simply cultivating one’s garden. Even if everything that traditional futurists have asked for is delivered – eternal youth, unlimited material wealth, morphological freedom, superintelligence, immersive VR, molecular nanotechnology, etc – there is no evidence that our subjective quality of life would on average significantly surpass the quality of life of our hunter-gatherer ancestors – or a New Guinea tribesman today – in the absence of reward pathway enrichment. This claim is difficult to prove in the absence of sophisticated neuroscanning; but objective indices of psychological distress e.g. suicide rates, bear it out. Unenhanced humans will still be prey to the spectrum of Darwinian emotions, ranging from terrible suffering to petty disappointments and frustrations – sadness, anxiety, jealousy, existential angst. Their biology is part of “what it means to be human”. Subjectively unpleasant states of consciousness exist because they were genetically adaptive. Each of our core emotions had a distinct signalling role in our evolutionary past: they tended to promote behaviours that enhanced the inclusive fitness of our genes in the ancestral environment.”[33]

Russian physicist and philosopher Victor Argonov argues that hedonism is not only a philosophical but also a verifiable scientific hypothesis. In 2014 he suggested “postulates of pleasure principle” confirmation of which would lead to a new scientific discipline, hedodynamics. Hedodynamics would be able to forecast the distant future development of human civilization and even the probable structure and psychology of other rational beings within the universe.[34] In order to build such a theory, science must discover the neural correlate of pleasure – neurophysiological parameter unambiguously corresponding to the feeling of pleasure (hedonic tone).

According to Argonov, posthumans will be able to reprogram their motivations in an arbitrary manner (to get pleasure from any programmed activity).[35] And if pleasure principle postulates are true, then general direction of civilization development is obvious: maximization of integral happiness in posthuman life (product of life span and average happiness). Posthumans will avoid constant pleasure stimulation, because it is incompatible with rational behavior required to prolong life. However, in average, they can become much happier than modern humans.

Many other aspects of posthuman society could be predicted by hedodynamics if the neural correlate of pleasure were discovered. For example, optimal number of individuals, their optimal body size (whether it matters for happiness or not) and the degree of aggression.

Critics of hedonism have objected to its exclusive concentration on pleasure as valuable.

In particular, G. E. Moore offered a thought experiment in criticism of pleasure as the sole bearer of value: he imagined two worldsone of exceeding beauty and the other a heap of filth. Neither of these worlds will be experienced by anyone. The question, then, is if it is better for the beautiful world to exist than the heap of filth. In this Moore implied that states of affairs have value beyond conscious pleasure, which he said spoke against the validity of hedonism.[36]

In Quran, God admonished mankind not to love the worldly pleasures, since it is related with greedy and source of sinful habit. He also threatened those who prefer worldly life rather than hereafter with Hell.

Those who choose the worldly life and its pleasures will be given proper recompense for their deeds in this life and will not suffer any loss. Such people will receive nothing in the next life except Hell fire. Their deeds will be made devoid of all virtue and their efforts will be in vain.

“Hedonism”. Encyclopdia Britannica (11th ed.). 1911.

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Hedonism – Wikipedia

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Caro Hedonista,De momento o nosso site est apenas dsponivel em Ingls.Contudo, a nossa equipa tem sua disposio alguem capaz de lhe responder em Portugus.Por favor no hesite em contactar directamente o nosso especialista, Miguel.

Chers Hdonistes, notre site internet nest disponible pour le moment quen Anglais. Cependant, notre quipe se tient votre disposition pour vous rpondre en Franais. Nhsitez pas contacter directement Maxime notre spcialiste francophone.

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Clothing Optional Resorts, Negril, Jamaica | Hedonism II

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hedonism | Philosophy & Definition | Britannica.com

Hedonism, in ethics, a general term for all theories of conduct in which the criterion is pleasure of one kind or another. The word is derived from the Greek hedone (pleasure), from hedys (sweet or pleasant).

Hedonistic theories of conduct have been held from the earliest times. They have been regularly misrepresented by their critics because of a simple misconception, namely, the assumption that the pleasure upheld by the hedonist is necessarily purely physical in its origins. This assumption is in most cases a complete perversion of the truth. Practically all hedonists recognize the existence of pleasures derived from fame and reputation, from friendship and sympathy, from knowledge and art. Most have urged that physical pleasures are not only ephemeral in themselves but also involve, either as prior conditions or as consequences, such pains as to discount any greater intensity that they may have while they last.

The earliest and most extreme form of hedonism is that of the Cyrenaics as stated by Aristippus, who argued that the goal of a good life should be the sentient pleasure of the moment. Since, as Protagoras maintained, knowledge is solely of momentary sensations, it is useless to try to calculate future pleasures and to balance pains against them. The true art of life is to crowd as much enjoyment as possible into each moment.

No school has been more subject to the misconception noted above than the Epicurean. Epicureanism is completely different from Cyrenaicism. For Epicurus pleasure was indeed the supreme good, but his interpretation of this maxim was profoundly influenced by the Socratic doctrine of prudence and Aristotles conception of the best life. The true hedonist would aim at a life of enduring pleasure, but this would be obtainable only under the guidance of reason. Self-control in the choice and limitation of pleasures with a view to reducing pain to a minimum was indispensable. This view informed the Epicurean maxim Of all this, the beginning, and the greatest good, is prudence. This negative side of Epicureanism developed to such an extent that some members of the school found the ideal life rather in indifference to pain than in positive enjoyment.

In the late 18th century Jeremy Bentham revived hedonism both as a psychological and as a moral theory under the umbrella of utilitarianism. Individuals have no goal other than the greatest pleasure, thus each person ought to pursue the greatest pleasure. It would seem to follow that each person inevitably always does what he or she ought. Bentham sought the solution to this paradox on different occasions in two incompatible directions. Sometimes he says that the act which one does is the act which one thinks will give the most pleasure, whereas the act which one ought to do is the act which really will provide the most pleasure. In short, calculation is salvation, while sin is shortsightedness. Alternatively he suggests that the act which one does is that which will give one the most pleasure, whereas the act one ought to do is that which will give all those affected by it the most pleasure.

The psychological doctrine that a humans only aim is pleasure was effectively attacked by Joseph Butler. He pointed out that each desire has its own specific object and that pleasure comes as a welcome addition or bonus when the desire achieves its object. Hence the paradox that the best way to get pleasure is to forget it and to pursue wholeheartedly other objects. Butler, however, went too far in maintaining that pleasure cannot be pursued as an end. Normally, indeed, when one is hungry or curious or lonely, there is desire to eat, to know, or to have company. These are not desires for pleasure. One can also eat sweets when one is not hungry, for the sake of the pleasure that they give.

Moral hedonism has been attacked since Socrates, though moralists sometimes have gone to the extreme of holding that humans never have a duty to bring about pleasure. It may seem odd to say that a human has a duty to pursue pleasure, but the pleasures of others certainly seem to count among the factors relevant in making a moral decision. One particular criticism which may be added to those usually urged against hedonists is that whereas they claim to simplify ethical problems by introducing a single standard, namely pleasure, in fact they have a double standard. As Bentham said, Nature has placed mankind under the governance of two sovereign masters, pain and pleasure. Hedonists tend to treat pleasure and pain as if they were, like heat and cold, degrees on a single scale, when they are really different in kind.

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Genetic Medicine Clinic at UWMC Home | UW Medicine

The Genetic Medicine Clinic at UWMC offers a full range of evaluation, diagnosis, assessment, genetic testing and interpretation, counseling and management. The clinic also provides referrals to appropriate resources for individuals with genetic disorders in their families or with disorders thought to have a genetic component.

In addition to general assessment, the medical genetics clinic team members have expertise in:

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Genetic predisposition – Wikipedia

A genetic predisposition is a genetic characteristic which influences the possible phenotypic development of an individual organism within a species or population under the influence of environmental conditions. In medicine, genetic susceptibility to a disease refers to a genetic predisposition to a health problem,[1] which may eventually be triggered by particular environmental or lifestyle factors, such as tobacco smoking or diet. Genetic testing is able to identify individuals who are genetically predisposed to certain diseases.

Predisposition is the capacity we are born with to learn things such as language and concept of self. Negative environmental influences may block the predisposition (ability) we have to do some things. Behaviors displayed by animals can be influenced by genetic predispositions. Genetic predisposition towards certain human behaviors is scientifically investigated by attempts to identify patterns of human behavior that seem to be invariant over long periods of time and in very different cultures.

For example, philosopher Daniel Dennett has proposed that humans are genetically predisposed to have a theory of mind because there has been evolutionary selection for the human ability to adopt the intentional stance.[1] The intentional stance is a useful behavioral strategy by which humans assume that others have minds like their own. This assumption allows you to predict the behavior of others based on personal knowledge of what you would do.

In 1951, Hans Eysenck and Donald Prell published an experiment in which identical (monozygotic) and fraternal (dizygotic) twins, ages 11 and 12, were tested for neuroticism. It is described in detail in an article published in the Journal of Mental Science. in which Eysenck and Prell concluded that, “The factor of neuroticism is not a statistical artifact, but constitutes a biological unit which is inherited as a whole….neurotic Genetic predisposition is to a large extent hereditarily determined.”[2]

E. O. Wilson’s book on sociobiology and his book Consilience discuss the idea of genetic predisposition to behaviors

The field of evolutionary psychology explores the idea that certain behaviors have been selected for during the course of evolution.

The Genetic Information Nondiscrimination Act, which was signed into law by President Bush on May 21, 2008,[3] prohibits discrimination in employment and health insurance based on genetic information.

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Genetic predisposition – Wikipedia

Genetic predisposition – Wikipedia

A genetic predisposition is a genetic characteristic which influences the possible phenotypic development of an individual organism within a species or population under the influence of environmental conditions. In medicine, genetic susceptibility to a disease refers to a genetic predisposition to a health problem,[1] which may eventually be triggered by particular environmental or lifestyle factors, such as tobacco smoking or diet. Genetic testing is able to identify individuals who are genetically predisposed to certain diseases.

Predisposition is the capacity we are born with to learn things such as language and concept of self. Negative environmental influences may block the predisposition (ability) we have to do some things. Behaviors displayed by animals can be influenced by genetic predispositions. Genetic predisposition towards certain human behaviors is scientifically investigated by attempts to identify patterns of human behavior that seem to be invariant over long periods of time and in very different cultures.

For example, philosopher Daniel Dennett has proposed that humans are genetically predisposed to have a theory of mind because there has been evolutionary selection for the human ability to adopt the intentional stance.[1] The intentional stance is a useful behavioral strategy by which humans assume that others have minds like their own. This assumption allows you to predict the behavior of others based on personal knowledge of what you would do.

In 1951, Hans Eysenck and Donald Prell published an experiment in which identical (monozygotic) and fraternal (dizygotic) twins, ages 11 and 12, were tested for neuroticism. It is described in detail in an article published in the Journal of Mental Science. in which Eysenck and Prell concluded that, “The factor of neuroticism is not a statistical artifact, but constitutes a biological unit which is inherited as a whole….neurotic Genetic predisposition is to a large extent hereditarily determined.”[2]

E. O. Wilson’s book on sociobiology and his book Consilience discuss the idea of genetic predisposition to behaviors

The field of evolutionary psychology explores the idea that certain behaviors have been selected for during the course of evolution.

The Genetic Information Nondiscrimination Act, which was signed into law by President Bush on May 21, 2008,[3] prohibits discrimination in employment and health insurance based on genetic information.

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Genetic predisposition – Wikipedia

Genetics – Wikipedia

This article is about the general scientific term. For the scientific journal, see Genetics (journal).

Genetics is the study of genes, genetic variation, and heredity in living organisms.[1][2] It is generally considered a field of biology, but intersects frequently with many other life sciences and is strongly linked with the study of information systems.

The father of genetics is Gregor Mendel, a late 19th-century scientist and Augustinian friar. Mendel studied “trait inheritance”, patterns in the way traits are handed down from parents to offspring. He observed that organisms (pea plants) inherit traits by way of discrete “units of inheritance”. This term, still used today, is a somewhat ambiguous definition of what is referred to as a gene.

Trait inheritance and molecular inheritance mechanisms of genes are still primary principles of genetics in the 21st century, but modern genetics has expanded beyond inheritance to studying the function and behavior of genes. Gene structure and function, variation, and distribution are studied within the context of the cell, the organism (e.g. dominance), and within the context of a population. Genetics has given rise to a number of subfields, including epigenetics and population genetics. Organisms studied within the broad field span the domains of life (archaea, bacteria, and eukarya).

Genetic processes work in combination with an organism’s environment and experiences to influence development and behavior, often referred to as nature versus nurture. The intracellular or extracellular environment of a cell or organism may switch gene transcription on or off. A classic example is two seeds of genetically identical corn, one placed in a temperate climate and one in an arid climate. While the average height of the two corn stalks may be genetically determined to be equal, the one in the arid climate only grows to half the height of the one in the temperate climate due to lack of water and nutrients in its environment.

The word genetics stems from the ancient Greek genetikos meaning “genitive”/”generative”, which in turn derives from genesis meaning “origin”.[3][4][5]

The observation that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding.[6] The modern science of genetics, seeking to understand this process, began with the work of the Augustinian friar Gregor Mendel in the mid-19th century.[7]

Prior to Mendel, Imre Festetics, a Hungarian noble, who lived in Kszeg before Mendel, was the first who used the word “genetics.” He described several rules of genetic inheritance in his work The genetic law of the Nature (Die genetische Gestze der Natur, 1819). His second law is the same as what Mendel published. In his third law, he developed the basic principles of mutation (he can be considered a forerunner of Hugo de Vries).[8]

Other theories of inheritance preceded Mendel’s work. A popular theory during the 19th century, and implied by Charles Darwin’s 1859 On the Origin of Species, was blending inheritance: the idea that individuals inherit a smooth blend of traits from their parents.[9] Mendel’s work provided examples where traits were definitely not blended after hybridization, showing that traits are produced by combinations of distinct genes rather than a continuous blend. Blending of traits in the progeny is now explained by the action of multiple genes with quantitative effects. Another theory that had some support at that time was the inheritance of acquired characteristics: the belief that individuals inherit traits strengthened by their parents. This theory (commonly associated with Jean-Baptiste Lamarck) is now known to be wrongthe experiences of individuals do not affect the genes they pass to their children,[10] although evidence in the field of epigenetics has revived some aspects of Lamarck’s theory.[11] Other theories included the pangenesis of Charles Darwin (which had both acquired and inherited aspects) and Francis Galton’s reformulation of pangenesis as both particulate and inherited.[12]

Modern genetics started with Mendel’s studies of the nature of inheritance in plants. In his paper “Versuche ber Pflanzenhybriden” (“Experiments on Plant Hybridization”), presented in 1865 to the Naturforschender Verein (Society for Research in Nature) in Brnn, Mendel traced the inheritance patterns of certain traits in pea plants and described them mathematically.[13] Although this pattern of inheritance could only be observed for a few traits, Mendel’s work suggested that heredity was particulate, not acquired, and that the inheritance patterns of many traits could be explained through simple rules and ratios.

The importance of Mendel’s work did not gain wide understanding until 1900, after his death, when Hugo de Vries and other scientists rediscovered his research. William Bateson, a proponent of Mendel’s work, coined the word genetics in 1905[14][15] (the adjective genetic, derived from the Greek word genesis, “origin”, predates the noun and was first used in a biological sense in 1860[16]). Bateson both acted as a mentor and was aided significantly by the work of female scientists from Newnham College at Cambridge, specifically the work of Becky Saunders, Nora Darwin Barlow, and Muriel Wheldale Onslow.[17] Bateson popularized the usage of the word genetics to describe the study of inheritance in his inaugural address to the Third International Conference on Plant Hybridization in London in 1906.[18]

After the rediscovery of Mendel’s work, scientists tried to determine which molecules in the cell were responsible for inheritance. In 1911, Thomas Hunt Morgan argued that genes are on chromosomes, based on observations of a sex-linked white eye mutation in fruit flies.[19] In 1913, his student Alfred Sturtevant used the phenomenon of genetic linkage to show that genes are arranged linearly on the chromosome.[20]

Although genes were known to exist on chromosomes, chromosomes are composed of both protein and DNA, and scientists did not know which of the two is responsible for inheritance. In 1928, Frederick Griffith discovered the phenomenon of transformation (see Griffith’s experiment): dead bacteria could transfer genetic material to “transform” other still-living bacteria. Sixteen years later, in 1944, the AveryMacLeodMcCarty experiment identified DNA as the molecule responsible for transformation.[21] The role of the nucleus as the repository of genetic information in eukaryotes had been established by Hmmerling in 1943 in his work on the single celled alga Acetabularia.[22] The HersheyChase experiment in 1952 confirmed that DNA (rather than protein) is the genetic material of the viruses that infect bacteria, providing further evidence that DNA is the molecule responsible for inheritance.[23]

James Watson and Francis Crick determined the structure of DNA in 1953, using the X-ray crystallography work of Rosalind Franklin and Maurice Wilkins that indicated DNA has a helical structure (i.e., shaped like a corkscrew).[24][25] Their double-helix model had two strands of DNA with the nucleotides pointing inward, each matching a complementary nucleotide on the other strand to form what look like rungs on a twisted ladder.[26] This structure showed that genetic information exists in the sequence of nucleotides on each strand of DNA. The structure also suggested a simple method for replication: if the strands are separated, new partner strands can be reconstructed for each based on the sequence of the old strand. This property is what gives DNA its semi-conservative nature where one strand of new DNA is from an original parent strand.[27]

Although the structure of DNA showed how inheritance works, it was still not known how DNA influences the behavior of cells. In the following years, scientists tried to understand how DNA controls the process of protein production.[28] It was discovered that the cell uses DNA as a template to create matching messenger RNA, molecules with nucleotides very similar to DNA. The nucleotide sequence of a messenger RNA is used to create an amino acid sequence in protein; this translation between nucleotide sequences and amino acid sequences is known as the genetic code.[29]

With the newfound molecular understanding of inheritance came an explosion of research.[30] A notable theory arose from Tomoko Ohta in 1973 with her amendment to the neutral theory of molecular evolution through publishing the nearly neutral theory of molecular evolution. In this theory, Ohta stressed the importance of natural selection and the environment to the rate at which genetic evolution occurs.[31] One important development was chain-termination DNA sequencing in 1977 by Frederick Sanger. This technology allows scientists to read the nucleotide sequence of a DNA molecule.[32] In 1983, Kary Banks Mullis developed the polymerase chain reaction, providing a quick way to isolate and amplify a specific section of DNA from a mixture.[33] The efforts of the Human Genome Project, Department of Energy, NIH, and parallel private efforts by Celera Genomics led to the sequencing of the human genome in 2003.[34][35]

At its most fundamental level, inheritance in organisms occurs by passing discrete heritable units, called genes, from parents to offspring.[36] This property was first observed by Gregor Mendel, who studied the segregation of heritable traits in pea plants.[13][37] In his experiments studying the trait for flower color, Mendel observed that the flowers of each pea plant were either purple or whitebut never an intermediate between the two colors. These different, discrete versions of the same gene are called alleles.

In the case of the pea, which is a diploid species, each individual plant has two copies of each gene, one copy inherited from each parent.[38] Many species, including humans, have this pattern of inheritance. Diploid organisms with two copies of the same allele of a given gene are called homozygous at that gene locus, while organisms with two different alleles of a given gene are called heterozygous.

The set of alleles for a given organism is called its genotype, while the observable traits of the organism are called its phenotype. When organisms are heterozygous at a gene, often one allele is called dominant as its qualities dominate the phenotype of the organism, while the other allele is called recessive as its qualities recede and are not observed. Some alleles do not have complete dominance and instead have incomplete dominance by expressing an intermediate phenotype, or codominance by expressing both alleles at once.[39]

When a pair of organisms reproduce sexually, their offspring randomly inherit one of the two alleles from each parent. These observations of discrete inheritance and the segregation of alleles are collectively known as Mendel’s first law or the Law of Segregation.

Geneticists use diagrams and symbols to describe inheritance. A gene is represented by one or a few letters. Often a “+” symbol is used to mark the usual, non-mutant allele for a gene.[40]

In fertilization and breeding experiments (and especially when discussing Mendel’s laws) the parents are referred to as the “P” generation and the offspring as the “F1” (first filial) generation. When the F1 offspring mate with each other, the offspring are called the “F2” (second filial) generation. One of the common diagrams used to predict the result of cross-breeding is the Punnett square.

When studying human genetic diseases, geneticists often use pedigree charts to represent the inheritance of traits.[41] These charts map the inheritance of a trait in a family tree.

Organisms have thousands of genes, and in sexually reproducing organisms these genes generally assort independently of each other. This means that the inheritance of an allele for yellow or green pea color is unrelated to the inheritance of alleles for white or purple flowers. This phenomenon, known as “Mendel’s second law” or the “law of independent assortment,” means that the alleles of different genes get shuffled between parents to form offspring with many different combinations. (Some genes do not assort independently, demonstrating genetic linkage, a topic discussed later in this article.)

Often different genes can interact in a way that influences the same trait. In the Blue-eyed Mary (Omphalodes verna), for example, there exists a gene with alleles that determine the color of flowers: blue or magenta. Another gene, however, controls whether the flowers have color at all or are white. When a plant has two copies of this white allele, its flowers are whiteregardless of whether the first gene has blue or magenta alleles. This interaction between genes is called epistasis, with the second gene epistatic to the first.[42]

Many traits are not discrete features (e.g. purple or white flowers) but are instead continuous features (e.g. human height and skin color). These complex traits are products of many genes.[43] The influence of these genes is mediated, to varying degrees, by the environment an organism has experienced. The degree to which an organism’s genes contribute to a complex trait is called heritability.[44] Measurement of the heritability of a trait is relativein a more variable environment, the environment has a bigger influence on the total variation of the trait. For example, human height is a trait with complex causes. It has a heritability of 89% in the United States. In Nigeria, however, where people experience a more variable access to good nutrition and health care, height has a heritability of only 62%.[45]

The molecular basis for genes is deoxyribonucleic acid (DNA). DNA is composed of a chain of nucleotides, of which there are four types: adenine (A), cytosine (C), guanine (G), and thymine (T). Genetic information exists in the sequence of these nucleotides, and genes exist as stretches of sequence along the DNA chain.[46] Viruses are the only exception to this rulesometimes viruses use the very similar molecule RNA instead of DNA as their genetic material.[47] Viruses cannot reproduce without a host and are unaffected by many genetic processes, so tend not to be considered living organisms.

DNA normally exists as a double-stranded molecule, coiled into the shape of a double helix. Each nucleotide in DNA preferentially pairs with its partner nucleotide on the opposite strand: A pairs with T, and C pairs with G. Thus, in its two-stranded form, each strand effectively contains all necessary information, redundant with its partner strand. This structure of DNA is the physical basis for inheritance: DNA replication duplicates the genetic information by splitting the strands and using each strand as a template for synthesis of a new partner strand.[48]

Genes are arranged linearly along long chains of DNA base-pair sequences. In bacteria, each cell usually contains a single circular genophore, while eukaryotic organisms (such as plants and animals) have their DNA arranged in multiple linear chromosomes. These DNA strands are often extremely long; the largest human chromosome, for example, is about 247 million base pairs in length.[49] The DNA of a chromosome is associated with structural proteins that organize, compact, and control access to the DNA, forming a material called chromatin; in eukaryotes, chromatin is usually composed of nucleosomes, segments of DNA wound around cores of histone proteins.[50] The full set of hereditary material in an organism (usually the combined DNA sequences of all chromosomes) is called the genome.

While haploid organisms have only one copy of each chromosome, most animals and many plants are diploid, containing two of each chromosome and thus two copies of every gene.[38] The two alleles for a gene are located on identical loci of the two homologous chromosomes, each allele inherited from a different parent.

Many species have so-called sex chromosomes that determine the gender of each organism.[51] In humans and many other animals, the Y chromosome contains the gene that triggers the development of the specifically male characteristics. In evolution, this chromosome has lost most of its content and also most of its genes, while the X chromosome is similar to the other chromosomes and contains many genes. The X and Y chromosomes form a strongly heterogeneous pair.

When cells divide, their full genome is copied and each daughter cell inherits one copy. This process, called mitosis, is the simplest form of reproduction and is the basis for asexual reproduction. Asexual reproduction can also occur in multicellular organisms, producing offspring that inherit their genome from a single parent. Offspring that are genetically identical to their parents are called clones.

Eukaryotic organisms often use sexual reproduction to generate offspring that contain a mixture of genetic material inherited from two different parents. The process of sexual reproduction alternates between forms that contain single copies of the genome (haploid) and double copies (diploid).[38] Haploid cells fuse and combine genetic material to create a diploid cell with paired chromosomes. Diploid organisms form haploids by dividing, without replicating their DNA, to create daughter cells that randomly inherit one of each pair of chromosomes. Most animals and many plants are diploid for most of their lifespan, with the haploid form reduced to single cell gametes such as sperm or eggs.

Although they do not use the haploid/diploid method of sexual reproduction, bacteria have many methods of acquiring new genetic information. Some bacteria can undergo conjugation, transferring a small circular piece of DNA to another bacterium.[52] Bacteria can also take up raw DNA fragments found in the environment and integrate them into their genomes, a phenomenon known as transformation.[53] These processes result in horizontal gene transfer, transmitting fragments of genetic information between organisms that would be otherwise unrelated.

The diploid nature of chromosomes allows for genes on different chromosomes to assort independently or be separated from their homologous pair during sexual reproduction wherein haploid gametes are formed. In this way new combinations of genes can occur in the offspring of a mating pair. Genes on the same chromosome would theoretically never recombine. However, they do, via the cellular process of chromosomal crossover. During crossover, chromosomes exchange stretches of DNA, effectively shuffling the gene alleles between the chromosomes.[54] This process of chromosomal crossover generally occurs during meiosis, a series of cell divisions that creates haploid cells.

The first cytological demonstration of crossing over was performed by Harriet Creighton and Barbara McClintock in 1931. Their research and experiments on corn provided cytological evidence for the genetic theory that linked genes on paired chromosomes do in fact exchange places from one homolog to the other.[55]

The probability of chromosomal crossover occurring between two given points on the chromosome is related to the distance between the points. For an arbitrarily long distance, the probability of crossover is high enough that the inheritance of the genes is effectively uncorrelated.[56] For genes that are closer together, however, the lower probability of crossover means that the genes demonstrate genetic linkage; alleles for the two genes tend to be inherited together. The amounts of linkage between a series of genes can be combined to form a linear linkage map that roughly describes the arrangement of the genes along the chromosome.[57]

Genes generally express their functional effect through the production of proteins, which are complex molecules responsible for most functions in the cell. Proteins are made up of one or more polypeptide chains, each of which is composed of a sequence of amino acids, and the DNA sequence of a gene (through an RNA intermediate) is used to produce a specific amino acid sequence. This process begins with the production of an RNA molecule with a sequence matching the gene’s DNA sequence, a process called transcription.

This messenger RNA molecule is then used to produce a corresponding amino acid sequence through a process called translation. Each group of three nucleotides in the sequence, called a codon, corresponds either to one of the twenty possible amino acids in a protein or an instruction to end the amino acid sequence; this correspondence is called the genetic code.[58] The flow of information is unidirectional: information is transferred from nucleotide sequences into the amino acid sequence of proteins, but it never transfers from protein back into the sequence of DNAa phenomenon Francis Crick called the central dogma of molecular biology.[59]

The specific sequence of amino acids results in a unique three-dimensional structure for that protein, and the three-dimensional structures of proteins are related to their functions.[60][61] Some are simple structural molecules, like the fibers formed by the protein collagen. Proteins can bind to other proteins and simple molecules, sometimes acting as enzymes by facilitating chemical reactions within the bound molecules (without changing the structure of the protein itself). Protein structure is dynamic; the protein hemoglobin bends into slightly different forms as it facilitates the capture, transport, and release of oxygen molecules within mammalian blood.

A single nucleotide difference within DNA can cause a change in the amino acid sequence of a protein. Because protein structures are the result of their amino acid sequences, some changes can dramatically change the properties of a protein by destabilizing the structure or changing the surface of the protein in a way that changes its interaction with other proteins and molecules. For example, sickle-cell anemia is a human genetic disease that results from a single base difference within the coding region for the -globin section of hemoglobin, causing a single amino acid change that changes hemoglobin’s physical properties.[62] Sickle-cell versions of hemoglobin stick to themselves, stacking to form fibers that distort the shape of red blood cells carrying the protein. These sickle-shaped cells no longer flow smoothly through blood vessels, having a tendency to clog or degrade, causing the medical problems associated with this disease.

Some DNA sequences are transcribed into RNA but are not translated into protein productssuch RNA molecules are called non-coding RNA. In some cases, these products fold into structures which are involved in critical cell functions (e.g. ribosomal RNA and transfer RNA). RNA can also have regulatory effects through hybridization interactions with other RNA molecules (e.g. microRNA).

Although genes contain all the information an organism uses to function, the environment plays an important role in determining the ultimate phenotypes an organism displays. The phrase “nature and nurture” refers to this complementary relationship. The phenotype of an organism depends on the interaction of genes and the environment. An interesting example is the coat coloration of the Siamese cat. In this case, the body temperature of the cat plays the role of the environment. The cat’s genes code for dark hair, thus the hair-producing cells in the cat make cellular proteins resulting in dark hair. But these dark hair-producing proteins are sensitive to temperature (i.e. have a mutation causing temperature-sensitivity) and denature in higher-temperature environments, failing to produce dark-hair pigment in areas where the cat has a higher body temperature. In a low-temperature environment, however, the protein’s structure is stable and produces dark-hair pigment normally. The protein remains functional in areas of skin that are coldersuch as its legs, ears, tail and faceso the cat has dark-hair at its extremities.[63]

Environment plays a major role in effects of the human genetic disease phenylketonuria.[64] The mutation that causes phenylketonuria disrupts the ability of the body to break down the amino acid phenylalanine, causing a toxic build-up of an intermediate molecule that, in turn, causes severe symptoms of progressive intellectual disability and seizures. However, if someone with the phenylketonuria mutation follows a strict diet that avoids this amino acid, they remain normal and healthy.

A common method for determining how genes and environment (“nature and nurture”) contribute to a phenotype involves studying identical and fraternal twins, or other siblings of multiple births.[65] Because identical siblings come from the same zygote, they are genetically the same. Fraternal twins are as genetically different from one another as normal siblings. By comparing how often a certain disorder occurs in a pair of identical twins to how often it occurs in a pair of fraternal twins, scientists can determine whether that disorder is caused by genetic or postnatal environmental factors whether it has “nature” or “nurture” causes. One famous example involved the study of the Genain quadruplets, who were identical quadruplets all diagnosed with schizophrenia.[66] However such tests cannot separate genetic factors from environmental factors affecting fetal development.

The genome of a given organism contains thousands of genes, but not all these genes need to be active at any given moment. A gene is expressed when it is being transcribed into mRNA and there exist many cellular methods of controlling the expression of genes such that proteins are produced only when needed by the cell. Transcription factors are regulatory proteins that bind to DNA, either promoting or inhibiting the transcription of a gene.[67] Within the genome of Escherichia coli bacteria, for example, there exists a series of genes necessary for the synthesis of the amino acid tryptophan. However, when tryptophan is already available to the cell, these genes for tryptophan synthesis are no longer needed. The presence of tryptophan directly affects the activity of the genestryptophan molecules bind to the tryptophan repressor (a transcription factor), changing the repressor’s structure such that the repressor binds to the genes. The tryptophan repressor blocks the transcription and expression of the genes, thereby creating negative feedback regulation of the tryptophan synthesis process.[68]

Differences in gene expression are especially clear within multicellular organisms, where cells all contain the same genome but have very different structures and behaviors due to the expression of different sets of genes. All the cells in a multicellular organism derive from a single cell, differentiating into variant cell types in response to external and intercellular signals and gradually establishing different patterns of gene expression to create different behaviors. As no single gene is responsible for the development of structures within multicellular organisms, these patterns arise from the complex interactions between many cells.

Within eukaryotes, there exist structural features of chromatin that influence the transcription of genes, often in the form of modifications to DNA and chromatin that are stably inherited by daughter cells.[69] These features are called “epigenetic” because they exist “on top” of the DNA sequence and retain inheritance from one cell generation to the next. Because of epigenetic features, different cell types grown within the same medium can retain very different properties. Although epigenetic features are generally dynamic over the course of development, some, like the phenomenon of paramutation, have multigenerational inheritance and exist as rare exceptions to the general rule of DNA as the basis for inheritance.[70]

During the process of DNA replication, errors occasionally occur in the polymerization of the second strand. These errors, called mutations, can affect the phenotype of an organism, especially if they occur within the protein coding sequence of a gene. Error rates are usually very low1 error in every 10100million basesdue to the “proofreading” ability of DNA polymerases.[71][72] Processes that increase the rate of changes in DNA are called mutagenic: mutagenic chemicals promote errors in DNA replication, often by interfering with the structure of base-pairing, while UV radiation induces mutations by causing damage to the DNA structure.[73] Chemical damage to DNA occurs naturally as well and cells use DNA repair mechanisms to repair mismatches and breaks. The repair does not, however, always restore the original sequence.

In organisms that use chromosomal crossover to exchange DNA and recombine genes, errors in alignment during meiosis can also cause mutations.[74] Errors in crossover are especially likely when similar sequences cause partner chromosomes to adopt a mistaken alignment; this makes some regions in genomes more prone to mutating in this way. These errors create large structural changes in DNA sequence duplications, inversions, deletions of entire regions or the accidental exchange of whole parts of sequences between different chromosomes (chromosomal translocation).

Mutations alter an organism’s genotype and occasionally this causes different phenotypes to appear. Most mutations have little effect on an organism’s phenotype, health, or reproductive fitness.[75] Mutations that do have an effect are usually detrimental, but occasionally some can be beneficial.[76] Studies in the fly Drosophila melanogaster suggest that if a mutation changes a protein produced by a gene, about 70 percent of these mutations will be harmful with the remainder being either neutral or weakly beneficial.[77]

Population genetics studies the distribution of genetic differences within populations and how these distributions change over time.[78] Changes in the frequency of an allele in a population are mainly influenced by natural selection, where a given allele provides a selective or reproductive advantage to the organism,[79] as well as other factors such as mutation, genetic drift, genetic hitchhiking,[80] artificial selection and migration.[81]

Over many generations, the genomes of organisms can change significantly, resulting in evolution. In the process called adaptation, selection for beneficial mutations can cause a species to evolve into forms better able to survive in their environment.[82] New species are formed through the process of speciation, often caused by geographical separations that prevent populations from exchanging genes with each other.[83]

By comparing the homology between different species’ genomes, it is possible to calculate the evolutionary distance between them and when they may have diverged. Genetic comparisons are generally considered a more accurate method of characterizing the relatedness between species than the comparison of phenotypic characteristics. The evolutionary distances between species can be used to form evolutionary trees; these trees represent the common descent and divergence of species over time, although they do not show the transfer of genetic material between unrelated species (known as horizontal gene transfer and most common in bacteria).[84]

Although geneticists originally studied inheritance in a wide range of organisms, researchers began to specialize in studying the genetics of a particular subset of organisms. The fact that significant research already existed for a given organism would encourage new researchers to choose it for further study, and so eventually a few model organisms became the basis for most genetics research.[85] Common research topics in model organism genetics include the study of gene regulation and the involvement of genes in development and cancer.

Organisms were chosen, in part, for convenienceshort generation times and easy genetic manipulation made some organisms popular genetics research tools. Widely used model organisms include the gut bacterium Escherichia coli, the plant Arabidopsis thaliana, baker’s yeast (Saccharomyces cerevisiae), the nematode Caenorhabditis elegans, the common fruit fly (Drosophila melanogaster), and the common house mouse (Mus musculus).

Medical genetics seeks to understand how genetic variation relates to human health and disease.[86] When searching for an unknown gene that may be involved in a disease, researchers commonly use genetic linkage and genetic pedigree charts to find the location on the genome associated with the disease. At the population level, researchers take advantage of Mendelian randomization to look for locations in the genome that are associated with diseases, a method especially useful for multigenic traits not clearly defined by a single gene.[87] Once a candidate gene is found, further research is often done on the corresponding (or homologous) genes of model organisms. In addition to studying genetic diseases, the increased availability of genotyping methods has led to the field of pharmacogenetics: the study of how genotype can affect drug responses.[88]

Individuals differ in their inherited tendency to develop cancer,[89] and cancer is a genetic disease.[90] The process of cancer development in the body is a combination of events. Mutations occasionally occur within cells in the body as they divide. Although these mutations will not be inherited by any offspring, they can affect the behavior of cells, sometimes causing them to grow and divide more frequently. There are biological mechanisms that attempt to stop this process; signals are given to inappropriately dividing cells that should trigger cell death, but sometimes additional mutations occur that cause cells to ignore these messages. An internal process of natural selection occurs within the body and eventually mutations accumulate within cells to promote their own growth, creating a cancerous tumor that grows and invades various tissues of the body.

Normally, a cell divides only in response to signals called growth factors and stops growing once in contact with surrounding cells and in response to growth-inhibitory signals. It usually then divides a limited number of times and dies, staying within the epithelium where it is unable to migrate to other organs. To become a cancer cell, a cell has to accumulate mutations in a number of genes (three to seven) that allow it to bypass this regulation: it no longer needs growth factors to divide, continues growing when making contact to neighbor cells, ignores inhibitory signals, keeps growing indefinitely and is immortal, escapes from the epithelium and ultimately may be able to escape from the primary tumor, cross the endothelium of a blood vessel, be transported by the bloodstream and colonize a new organ, forming deadly metastasis. Although there are some genetic predispositions in a small fraction of cancers, the major fraction is due to a set of new genetic mutations that originally appear and accumulate in one or a small number of cells that will divide to form the tumor and are not transmitted to the progeny (somatic mutations). The most frequent mutations are a loss of function of p53 protein, a tumor suppressor, or in the p53 pathway, and gain of function mutations in the Ras proteins, or in other oncogenes.

DNA can be manipulated in the laboratory. Restriction enzymes are commonly used enzymes that cut DNA at specific sequences, producing predictable fragments of DNA.[91] DNA fragments can be visualized through use of gel electrophoresis, which separates fragments according to their length.

The use of ligation enzymes allows DNA fragments to be connected. By binding (“ligating”) fragments of DNA together from different sources, researchers can create recombinant DNA, the DNA often associated with genetically modified organisms. Recombinant DNA is commonly used in the context of plasmids: short circular DNA molecules with a few genes on them. In the process known as molecular cloning, researchers can amplify the DNA fragments by inserting plasmids into bacteria and then culturing them on plates of agar (to isolate clones of bacteria cells “cloning” can also refer to the various means of creating cloned (“clonal”) organisms).

DNA can also be amplified using a procedure called the polymerase chain reaction (PCR).[92] By using specific short sequences of DNA, PCR can isolate and exponentially amplify a targeted region of DNA. Because it can amplify from extremely small amounts of DNA, PCR is also often used to detect the presence of specific DNA sequences.

DNA sequencing, one of the most fundamental technologies developed to study genetics, allows researchers to determine the sequence of nucleotides in DNA fragments. The technique of chain-termination sequencing, developed in 1977 by a team led by Frederick Sanger, is still routinely used to sequence DNA fragments.[93] Using this technology, researchers have been able to study the molecular sequences associated with many human diseases.

As sequencing has become less expensive, researchers have sequenced the genomes of many organisms using a process called genome assembly, which utilizes computational tools to stitch together sequences from many different fragments.[94] These technologies were used to sequence the human genome in the Human Genome Project completed in 2003.[34] New high-throughput sequencing technologies are dramatically lowering the cost of DNA sequencing, with many researchers hoping to bring the cost of resequencing a human genome down to a thousand dollars.[95]

Next-generation sequencing (or high-throughput sequencing) came about due to the ever-increasing demand for low-cost sequencing. These sequencing technologies allow the production of potentially millions of sequences concurrently.[96][97] The large amount of sequence data available has created the field of genomics, research that uses computational tools to search for and analyze patterns in the full genomes of organisms. Genomics can also be considered a subfield of bioinformatics, which uses computational approaches to analyze large sets of biological data. A common problem to these fields of research is how to manage and share data that deals with human subject and personally identifiable information. See also genomics data sharing.

On 19 March 2015, a group of leading biologists urged a worldwide ban on clinical use of methods, particularly the use of CRISPR and zinc finger, to edit the human genome in a way that can be inherited.[98][99][100][101] In April 2015, Chinese researchers reported results of basic research to edit the DNA of non-viable human embryos using CRISPR.[102][103]

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Genetics – Wikipedia

Genetics – Wikipedia

This article is about the general scientific term. For the scientific journal, see Genetics (journal).

Genetics is the study of genes, genetic variation, and heredity in living organisms.[1][2] It is generally considered a field of biology, but intersects frequently with many other life sciences and is strongly linked with the study of information systems.

The father of genetics is Gregor Mendel, a late 19th-century scientist and Augustinian friar. Mendel studied “trait inheritance”, patterns in the way traits are handed down from parents to offspring. He observed that organisms (pea plants) inherit traits by way of discrete “units of inheritance”. This term, still used today, is a somewhat ambiguous definition of what is referred to as a gene.

Trait inheritance and molecular inheritance mechanisms of genes are still primary principles of genetics in the 21st century, but modern genetics has expanded beyond inheritance to studying the function and behavior of genes. Gene structure and function, variation, and distribution are studied within the context of the cell, the organism (e.g. dominance), and within the context of a population. Genetics has given rise to a number of subfields, including epigenetics and population genetics. Organisms studied within the broad field span the domains of life (archaea, bacteria, and eukarya).

Genetic processes work in combination with an organism’s environment and experiences to influence development and behavior, often referred to as nature versus nurture. The intracellular or extracellular environment of a cell or organism may switch gene transcription on or off. A classic example is two seeds of genetically identical corn, one placed in a temperate climate and one in an arid climate. While the average height of the two corn stalks may be genetically determined to be equal, the one in the arid climate only grows to half the height of the one in the temperate climate due to lack of water and nutrients in its environment.

The word genetics stems from the ancient Greek genetikos meaning “genitive”/”generative”, which in turn derives from genesis meaning “origin”.[3][4][5]

The observation that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding.[6] The modern science of genetics, seeking to understand this process, began with the work of the Augustinian friar Gregor Mendel in the mid-19th century.[7]

Prior to Mendel, Imre Festetics, a Hungarian noble, who lived in Kszeg before Mendel, was the first who used the word “genetics.” He described several rules of genetic inheritance in his work The genetic law of the Nature (Die genetische Gestze der Natur, 1819). His second law is the same as what Mendel published. In his third law, he developed the basic principles of mutation (he can be considered a forerunner of Hugo de Vries).[8]

Other theories of inheritance preceded Mendel’s work. A popular theory during the 19th century, and implied by Charles Darwin’s 1859 On the Origin of Species, was blending inheritance: the idea that individuals inherit a smooth blend of traits from their parents.[9] Mendel’s work provided examples where traits were definitely not blended after hybridization, showing that traits are produced by combinations of distinct genes rather than a continuous blend. Blending of traits in the progeny is now explained by the action of multiple genes with quantitative effects. Another theory that had some support at that time was the inheritance of acquired characteristics: the belief that individuals inherit traits strengthened by their parents. This theory (commonly associated with Jean-Baptiste Lamarck) is now known to be wrongthe experiences of individuals do not affect the genes they pass to their children,[10] although evidence in the field of epigenetics has revived some aspects of Lamarck’s theory.[11] Other theories included the pangenesis of Charles Darwin (which had both acquired and inherited aspects) and Francis Galton’s reformulation of pangenesis as both particulate and inherited.[12]

Modern genetics started with Mendel’s studies of the nature of inheritance in plants. In his paper “Versuche ber Pflanzenhybriden” (“Experiments on Plant Hybridization”), presented in 1865 to the Naturforschender Verein (Society for Research in Nature) in Brnn, Mendel traced the inheritance patterns of certain traits in pea plants and described them mathematically.[13] Although this pattern of inheritance could only be observed for a few traits, Mendel’s work suggested that heredity was particulate, not acquired, and that the inheritance patterns of many traits could be explained through simple rules and ratios.

The importance of Mendel’s work did not gain wide understanding until 1900, after his death, when Hugo de Vries and other scientists rediscovered his research. William Bateson, a proponent of Mendel’s work, coined the word genetics in 1905[14][15] (the adjective genetic, derived from the Greek word genesis, “origin”, predates the noun and was first used in a biological sense in 1860[16]). Bateson both acted as a mentor and was aided significantly by the work of female scientists from Newnham College at Cambridge, specifically the work of Becky Saunders, Nora Darwin Barlow, and Muriel Wheldale Onslow.[17] Bateson popularized the usage of the word genetics to describe the study of inheritance in his inaugural address to the Third International Conference on Plant Hybridization in London in 1906.[18]

After the rediscovery of Mendel’s work, scientists tried to determine which molecules in the cell were responsible for inheritance. In 1911, Thomas Hunt Morgan argued that genes are on chromosomes, based on observations of a sex-linked white eye mutation in fruit flies.[19] In 1913, his student Alfred Sturtevant used the phenomenon of genetic linkage to show that genes are arranged linearly on the chromosome.[20]

Although genes were known to exist on chromosomes, chromosomes are composed of both protein and DNA, and scientists did not know which of the two is responsible for inheritance. In 1928, Frederick Griffith discovered the phenomenon of transformation (see Griffith’s experiment): dead bacteria could transfer genetic material to “transform” other still-living bacteria. Sixteen years later, in 1944, the AveryMacLeodMcCarty experiment identified DNA as the molecule responsible for transformation.[21] The role of the nucleus as the repository of genetic information in eukaryotes had been established by Hmmerling in 1943 in his work on the single celled alga Acetabularia.[22] The HersheyChase experiment in 1952 confirmed that DNA (rather than protein) is the genetic material of the viruses that infect bacteria, providing further evidence that DNA is the molecule responsible for inheritance.[23]

James Watson and Francis Crick determined the structure of DNA in 1953, using the X-ray crystallography work of Rosalind Franklin and Maurice Wilkins that indicated DNA has a helical structure (i.e., shaped like a corkscrew).[24][25] Their double-helix model had two strands of DNA with the nucleotides pointing inward, each matching a complementary nucleotide on the other strand to form what look like rungs on a twisted ladder.[26] This structure showed that genetic information exists in the sequence of nucleotides on each strand of DNA. The structure also suggested a simple method for replication: if the strands are separated, new partner strands can be reconstructed for each based on the sequence of the old strand. This property is what gives DNA its semi-conservative nature where one strand of new DNA is from an original parent strand.[27]

Although the structure of DNA showed how inheritance works, it was still not known how DNA influences the behavior of cells. In the following years, scientists tried to understand how DNA controls the process of protein production.[28] It was discovered that the cell uses DNA as a template to create matching messenger RNA, molecules with nucleotides very similar to DNA. The nucleotide sequence of a messenger RNA is used to create an amino acid sequence in protein; this translation between nucleotide sequences and amino acid sequences is known as the genetic code.[29]

With the newfound molecular understanding of inheritance came an explosion of research.[30] A notable theory arose from Tomoko Ohta in 1973 with her amendment to the neutral theory of molecular evolution through publishing the nearly neutral theory of molecular evolution. In this theory, Ohta stressed the importance of natural selection and the environment to the rate at which genetic evolution occurs.[31] One important development was chain-termination DNA sequencing in 1977 by Frederick Sanger. This technology allows scientists to read the nucleotide sequence of a DNA molecule.[32] In 1983, Kary Banks Mullis developed the polymerase chain reaction, providing a quick way to isolate and amplify a specific section of DNA from a mixture.[33] The efforts of the Human Genome Project, Department of Energy, NIH, and parallel private efforts by Celera Genomics led to the sequencing of the human genome in 2003.[34][35]

At its most fundamental level, inheritance in organisms occurs by passing discrete heritable units, called genes, from parents to offspring.[36] This property was first observed by Gregor Mendel, who studied the segregation of heritable traits in pea plants.[13][37] In his experiments studying the trait for flower color, Mendel observed that the flowers of each pea plant were either purple or whitebut never an intermediate between the two colors. These different, discrete versions of the same gene are called alleles.

In the case of the pea, which is a diploid species, each individual plant has two copies of each gene, one copy inherited from each parent.[38] Many species, including humans, have this pattern of inheritance. Diploid organisms with two copies of the same allele of a given gene are called homozygous at that gene locus, while organisms with two different alleles of a given gene are called heterozygous.

The set of alleles for a given organism is called its genotype, while the observable traits of the organism are called its phenotype. When organisms are heterozygous at a gene, often one allele is called dominant as its qualities dominate the phenotype of the organism, while the other allele is called recessive as its qualities recede and are not observed. Some alleles do not have complete dominance and instead have incomplete dominance by expressing an intermediate phenotype, or codominance by expressing both alleles at once.[39]

When a pair of organisms reproduce sexually, their offspring randomly inherit one of the two alleles from each parent. These observations of discrete inheritance and the segregation of alleles are collectively known as Mendel’s first law or the Law of Segregation.

Geneticists use diagrams and symbols to describe inheritance. A gene is represented by one or a few letters. Often a “+” symbol is used to mark the usual, non-mutant allele for a gene.[40]

In fertilization and breeding experiments (and especially when discussing Mendel’s laws) the parents are referred to as the “P” generation and the offspring as the “F1” (first filial) generation. When the F1 offspring mate with each other, the offspring are called the “F2” (second filial) generation. One of the common diagrams used to predict the result of cross-breeding is the Punnett square.

When studying human genetic diseases, geneticists often use pedigree charts to represent the inheritance of traits.[41] These charts map the inheritance of a trait in a family tree.

Organisms have thousands of genes, and in sexually reproducing organisms these genes generally assort independently of each other. This means that the inheritance of an allele for yellow or green pea color is unrelated to the inheritance of alleles for white or purple flowers. This phenomenon, known as “Mendel’s second law” or the “law of independent assortment,” means that the alleles of different genes get shuffled between parents to form offspring with many different combinations. (Some genes do not assort independently, demonstrating genetic linkage, a topic discussed later in this article.)

Often different genes can interact in a way that influences the same trait. In the Blue-eyed Mary (Omphalodes verna), for example, there exists a gene with alleles that determine the color of flowers: blue or magenta. Another gene, however, controls whether the flowers have color at all or are white. When a plant has two copies of this white allele, its flowers are whiteregardless of whether the first gene has blue or magenta alleles. This interaction between genes is called epistasis, with the second gene epistatic to the first.[42]

Many traits are not discrete features (e.g. purple or white flowers) but are instead continuous features (e.g. human height and skin color). These complex traits are products of many genes.[43] The influence of these genes is mediated, to varying degrees, by the environment an organism has experienced. The degree to which an organism’s genes contribute to a complex trait is called heritability.[44] Measurement of the heritability of a trait is relativein a more variable environment, the environment has a bigger influence on the total variation of the trait. For example, human height is a trait with complex causes. It has a heritability of 89% in the United States. In Nigeria, however, where people experience a more variable access to good nutrition and health care, height has a heritability of only 62%.[45]

The molecular basis for genes is deoxyribonucleic acid (DNA). DNA is composed of a chain of nucleotides, of which there are four types: adenine (A), cytosine (C), guanine (G), and thymine (T). Genetic information exists in the sequence of these nucleotides, and genes exist as stretches of sequence along the DNA chain.[46] Viruses are the only exception to this rulesometimes viruses use the very similar molecule RNA instead of DNA as their genetic material.[47] Viruses cannot reproduce without a host and are unaffected by many genetic processes, so tend not to be considered living organisms.

DNA normally exists as a double-stranded molecule, coiled into the shape of a double helix. Each nucleotide in DNA preferentially pairs with its partner nucleotide on the opposite strand: A pairs with T, and C pairs with G. Thus, in its two-stranded form, each strand effectively contains all necessary information, redundant with its partner strand. This structure of DNA is the physical basis for inheritance: DNA replication duplicates the genetic information by splitting the strands and using each strand as a template for synthesis of a new partner strand.[48]

Genes are arranged linearly along long chains of DNA base-pair sequences. In bacteria, each cell usually contains a single circular genophore, while eukaryotic organisms (such as plants and animals) have their DNA arranged in multiple linear chromosomes. These DNA strands are often extremely long; the largest human chromosome, for example, is about 247 million base pairs in length.[49] The DNA of a chromosome is associated with structural proteins that organize, compact, and control access to the DNA, forming a material called chromatin; in eukaryotes, chromatin is usually composed of nucleosomes, segments of DNA wound around cores of histone proteins.[50] The full set of hereditary material in an organism (usually the combined DNA sequences of all chromosomes) is called the genome.

While haploid organisms have only one copy of each chromosome, most animals and many plants are diploid, containing two of each chromosome and thus two copies of every gene.[38] The two alleles for a gene are located on identical loci of the two homologous chromosomes, each allele inherited from a different parent.

Many species have so-called sex chromosomes that determine the gender of each organism.[51] In humans and many other animals, the Y chromosome contains the gene that triggers the development of the specifically male characteristics. In evolution, this chromosome has lost most of its content and also most of its genes, while the X chromosome is similar to the other chromosomes and contains many genes. The X and Y chromosomes form a strongly heterogeneous pair.

When cells divide, their full genome is copied and each daughter cell inherits one copy. This process, called mitosis, is the simplest form of reproduction and is the basis for asexual reproduction. Asexual reproduction can also occur in multicellular organisms, producing offspring that inherit their genome from a single parent. Offspring that are genetically identical to their parents are called clones.

Eukaryotic organisms often use sexual reproduction to generate offspring that contain a mixture of genetic material inherited from two different parents. The process of sexual reproduction alternates between forms that contain single copies of the genome (haploid) and double copies (diploid).[38] Haploid cells fuse and combine genetic material to create a diploid cell with paired chromosomes. Diploid organisms form haploids by dividing, without replicating their DNA, to create daughter cells that randomly inherit one of each pair of chromosomes. Most animals and many plants are diploid for most of their lifespan, with the haploid form reduced to single cell gametes such as sperm or eggs.

Although they do not use the haploid/diploid method of sexual reproduction, bacteria have many methods of acquiring new genetic information. Some bacteria can undergo conjugation, transferring a small circular piece of DNA to another bacterium.[52] Bacteria can also take up raw DNA fragments found in the environment and integrate them into their genomes, a phenomenon known as transformation.[53] These processes result in horizontal gene transfer, transmitting fragments of genetic information between organisms that would be otherwise unrelated.

The diploid nature of chromosomes allows for genes on different chromosomes to assort independently or be separated from their homologous pair during sexual reproduction wherein haploid gametes are formed. In this way new combinations of genes can occur in the offspring of a mating pair. Genes on the same chromosome would theoretically never recombine. However, they do, via the cellular process of chromosomal crossover. During crossover, chromosomes exchange stretches of DNA, effectively shuffling the gene alleles between the chromosomes.[54] This process of chromosomal crossover generally occurs during meiosis, a series of cell divisions that creates haploid cells.

The first cytological demonstration of crossing over was performed by Harriet Creighton and Barbara McClintock in 1931. Their research and experiments on corn provided cytological evidence for the genetic theory that linked genes on paired chromosomes do in fact exchange places from one homolog to the other.[55]

The probability of chromosomal crossover occurring between two given points on the chromosome is related to the distance between the points. For an arbitrarily long distance, the probability of crossover is high enough that the inheritance of the genes is effectively uncorrelated.[56] For genes that are closer together, however, the lower probability of crossover means that the genes demonstrate genetic linkage; alleles for the two genes tend to be inherited together. The amounts of linkage between a series of genes can be combined to form a linear linkage map that roughly describes the arrangement of the genes along the chromosome.[57]

Genes generally express their functional effect through the production of proteins, which are complex molecules responsible for most functions in the cell. Proteins are made up of one or more polypeptide chains, each of which is composed of a sequence of amino acids, and the DNA sequence of a gene (through an RNA intermediate) is used to produce a specific amino acid sequence. This process begins with the production of an RNA molecule with a sequence matching the gene’s DNA sequence, a process called transcription.

This messenger RNA molecule is then used to produce a corresponding amino acid sequence through a process called translation. Each group of three nucleotides in the sequence, called a codon, corresponds either to one of the twenty possible amino acids in a protein or an instruction to end the amino acid sequence; this correspondence is called the genetic code.[58] The flow of information is unidirectional: information is transferred from nucleotide sequences into the amino acid sequence of proteins, but it never transfers from protein back into the sequence of DNAa phenomenon Francis Crick called the central dogma of molecular biology.[59]

The specific sequence of amino acids results in a unique three-dimensional structure for that protein, and the three-dimensional structures of proteins are related to their functions.[60][61] Some are simple structural molecules, like the fibers formed by the protein collagen. Proteins can bind to other proteins and simple molecules, sometimes acting as enzymes by facilitating chemical reactions within the bound molecules (without changing the structure of the protein itself). Protein structure is dynamic; the protein hemoglobin bends into slightly different forms as it facilitates the capture, transport, and release of oxygen molecules within mammalian blood.

A single nucleotide difference within DNA can cause a change in the amino acid sequence of a protein. Because protein structures are the result of their amino acid sequences, some changes can dramatically change the properties of a protein by destabilizing the structure or changing the surface of the protein in a way that changes its interaction with other proteins and molecules. For example, sickle-cell anemia is a human genetic disease that results from a single base difference within the coding region for the -globin section of hemoglobin, causing a single amino acid change that changes hemoglobin’s physical properties.[62] Sickle-cell versions of hemoglobin stick to themselves, stacking to form fibers that distort the shape of red blood cells carrying the protein. These sickle-shaped cells no longer flow smoothly through blood vessels, having a tendency to clog or degrade, causing the medical problems associated with this disease.

Some DNA sequences are transcribed into RNA but are not translated into protein productssuch RNA molecules are called non-coding RNA. In some cases, these products fold into structures which are involved in critical cell functions (e.g. ribosomal RNA and transfer RNA). RNA can also have regulatory effects through hybridization interactions with other RNA molecules (e.g. microRNA).

Although genes contain all the information an organism uses to function, the environment plays an important role in determining the ultimate phenotypes an organism displays. The phrase “nature and nurture” refers to this complementary relationship. The phenotype of an organism depends on the interaction of genes and the environment. An interesting example is the coat coloration of the Siamese cat. In this case, the body temperature of the cat plays the role of the environment. The cat’s genes code for dark hair, thus the hair-producing cells in the cat make cellular proteins resulting in dark hair. But these dark hair-producing proteins are sensitive to temperature (i.e. have a mutation causing temperature-sensitivity) and denature in higher-temperature environments, failing to produce dark-hair pigment in areas where the cat has a higher body temperature. In a low-temperature environment, however, the protein’s structure is stable and produces dark-hair pigment normally. The protein remains functional in areas of skin that are coldersuch as its legs, ears, tail and faceso the cat has dark-hair at its extremities.[63]

Environment plays a major role in effects of the human genetic disease phenylketonuria.[64] The mutation that causes phenylketonuria disrupts the ability of the body to break down the amino acid phenylalanine, causing a toxic build-up of an intermediate molecule that, in turn, causes severe symptoms of progressive intellectual disability and seizures. However, if someone with the phenylketonuria mutation follows a strict diet that avoids this amino acid, they remain normal and healthy.

A common method for determining how genes and environment (“nature and nurture”) contribute to a phenotype involves studying identical and fraternal twins, or other siblings of multiple births.[65] Because identical siblings come from the same zygote, they are genetically the same. Fraternal twins are as genetically different from one another as normal siblings. By comparing how often a certain disorder occurs in a pair of identical twins to how often it occurs in a pair of fraternal twins, scientists can determine whether that disorder is caused by genetic or postnatal environmental factors whether it has “nature” or “nurture” causes. One famous example involved the study of the Genain quadruplets, who were identical quadruplets all diagnosed with schizophrenia.[66] However such tests cannot separate genetic factors from environmental factors affecting fetal development.

The genome of a given organism contains thousands of genes, but not all these genes need to be active at any given moment. A gene is expressed when it is being transcribed into mRNA and there exist many cellular methods of controlling the expression of genes such that proteins are produced only when needed by the cell. Transcription factors are regulatory proteins that bind to DNA, either promoting or inhibiting the transcription of a gene.[67] Within the genome of Escherichia coli bacteria, for example, there exists a series of genes necessary for the synthesis of the amino acid tryptophan. However, when tryptophan is already available to the cell, these genes for tryptophan synthesis are no longer needed. The presence of tryptophan directly affects the activity of the genestryptophan molecules bind to the tryptophan repressor (a transcription factor), changing the repressor’s structure such that the repressor binds to the genes. The tryptophan repressor blocks the transcription and expression of the genes, thereby creating negative feedback regulation of the tryptophan synthesis process.[68]

Differences in gene expression are especially clear within multicellular organisms, where cells all contain the same genome but have very different structures and behaviors due to the expression of different sets of genes. All the cells in a multicellular organism derive from a single cell, differentiating into variant cell types in response to external and intercellular signals and gradually establishing different patterns of gene expression to create different behaviors. As no single gene is responsible for the development of structures within multicellular organisms, these patterns arise from the complex interactions between many cells.

Within eukaryotes, there exist structural features of chromatin that influence the transcription of genes, often in the form of modifications to DNA and chromatin that are stably inherited by daughter cells.[69] These features are called “epigenetic” because they exist “on top” of the DNA sequence and retain inheritance from one cell generation to the next. Because of epigenetic features, different cell types grown within the same medium can retain very different properties. Although epigenetic features are generally dynamic over the course of development, some, like the phenomenon of paramutation, have multigenerational inheritance and exist as rare exceptions to the general rule of DNA as the basis for inheritance.[70]

During the process of DNA replication, errors occasionally occur in the polymerization of the second strand. These errors, called mutations, can affect the phenotype of an organism, especially if they occur within the protein coding sequence of a gene. Error rates are usually very low1 error in every 10100million basesdue to the “proofreading” ability of DNA polymerases.[71][72] Processes that increase the rate of changes in DNA are called mutagenic: mutagenic chemicals promote errors in DNA replication, often by interfering with the structure of base-pairing, while UV radiation induces mutations by causing damage to the DNA structure.[73] Chemical damage to DNA occurs naturally as well and cells use DNA repair mechanisms to repair mismatches and breaks. The repair does not, however, always restore the original sequence.

In organisms that use chromosomal crossover to exchange DNA and recombine genes, errors in alignment during meiosis can also cause mutations.[74] Errors in crossover are especially likely when similar sequences cause partner chromosomes to adopt a mistaken alignment; this makes some regions in genomes more prone to mutating in this way. These errors create large structural changes in DNA sequence duplications, inversions, deletions of entire regions or the accidental exchange of whole parts of sequences between different chromosomes (chromosomal translocation).

Mutations alter an organism’s genotype and occasionally this causes different phenotypes to appear. Most mutations have little effect on an organism’s phenotype, health, or reproductive fitness.[75] Mutations that do have an effect are usually detrimental, but occasionally some can be beneficial.[76] Studies in the fly Drosophila melanogaster suggest that if a mutation changes a protein produced by a gene, about 70 percent of these mutations will be harmful with the remainder being either neutral or weakly beneficial.[77]

Population genetics studies the distribution of genetic differences within populations and how these distributions change over time.[78] Changes in the frequency of an allele in a population are mainly influenced by natural selection, where a given allele provides a selective or reproductive advantage to the organism,[79] as well as other factors such as mutation, genetic drift, genetic hitchhiking,[80] artificial selection and migration.[81]

Over many generations, the genomes of organisms can change significantly, resulting in evolution. In the process called adaptation, selection for beneficial mutations can cause a species to evolve into forms better able to survive in their environment.[82] New species are formed through the process of speciation, often caused by geographical separations that prevent populations from exchanging genes with each other.[83]

By comparing the homology between different species’ genomes, it is possible to calculate the evolutionary distance between them and when they may have diverged. Genetic comparisons are generally considered a more accurate method of characterizing the relatedness between species than the comparison of phenotypic characteristics. The evolutionary distances between species can be used to form evolutionary trees; these trees represent the common descent and divergence of species over time, although they do not show the transfer of genetic material between unrelated species (known as horizontal gene transfer and most common in bacteria).[84]

Although geneticists originally studied inheritance in a wide range of organisms, researchers began to specialize in studying the genetics of a particular subset of organisms. The fact that significant research already existed for a given organism would encourage new researchers to choose it for further study, and so eventually a few model organisms became the basis for most genetics research.[85] Common research topics in model organism genetics include the study of gene regulation and the involvement of genes in development and cancer.

Organisms were chosen, in part, for convenienceshort generation times and easy genetic manipulation made some organisms popular genetics research tools. Widely used model organisms include the gut bacterium Escherichia coli, the plant Arabidopsis thaliana, baker’s yeast (Saccharomyces cerevisiae), the nematode Caenorhabditis elegans, the common fruit fly (Drosophila melanogaster), and the common house mouse (Mus musculus).

Medical genetics seeks to understand how genetic variation relates to human health and disease.[86] When searching for an unknown gene that may be involved in a disease, researchers commonly use genetic linkage and genetic pedigree charts to find the location on the genome associated with the disease. At the population level, researchers take advantage of Mendelian randomization to look for locations in the genome that are associated with diseases, a method especially useful for multigenic traits not clearly defined by a single gene.[87] Once a candidate gene is found, further research is often done on the corresponding (or homologous) genes of model organisms. In addition to studying genetic diseases, the increased availability of genotyping methods has led to the field of pharmacogenetics: the study of how genotype can affect drug responses.[88]

Individuals differ in their inherited tendency to develop cancer,[89] and cancer is a genetic disease.[90] The process of cancer development in the body is a combination of events. Mutations occasionally occur within cells in the body as they divide. Although these mutations will not be inherited by any offspring, they can affect the behavior of cells, sometimes causing them to grow and divide more frequently. There are biological mechanisms that attempt to stop this process; signals are given to inappropriately dividing cells that should trigger cell death, but sometimes additional mutations occur that cause cells to ignore these messages. An internal process of natural selection occurs within the body and eventually mutations accumulate within cells to promote their own growth, creating a cancerous tumor that grows and invades various tissues of the body.

Normally, a cell divides only in response to signals called growth factors and stops growing once in contact with surrounding cells and in response to growth-inhibitory signals. It usually then divides a limited number of times and dies, staying within the epithelium where it is unable to migrate to other organs. To become a cancer cell, a cell has to accumulate mutations in a number of genes (three to seven) that allow it to bypass this regulation: it no longer needs growth factors to divide, continues growing when making contact to neighbor cells, ignores inhibitory signals, keeps growing indefinitely and is immortal, escapes from the epithelium and ultimately may be able to escape from the primary tumor, cross the endothelium of a blood vessel, be transported by the bloodstream and colonize a new organ, forming deadly metastasis. Although there are some genetic predispositions in a small fraction of cancers, the major fraction is due to a set of new genetic mutations that originally appear and accumulate in one or a small number of cells that will divide to form the tumor and are not transmitted to the progeny (somatic mutations). The most frequent mutations are a loss of function of p53 protein, a tumor suppressor, or in the p53 pathway, and gain of function mutations in the Ras proteins, or in other oncogenes.

DNA can be manipulated in the laboratory. Restriction enzymes are commonly used enzymes that cut DNA at specific sequences, producing predictable fragments of DNA.[91] DNA fragments can be visualized through use of gel electrophoresis, which separates fragments according to their length.

The use of ligation enzymes allows DNA fragments to be connected. By binding (“ligating”) fragments of DNA together from different sources, researchers can create recombinant DNA, the DNA often associated with genetically modified organisms. Recombinant DNA is commonly used in the context of plasmids: short circular DNA molecules with a few genes on them. In the process known as molecular cloning, researchers can amplify the DNA fragments by inserting plasmids into bacteria and then culturing them on plates of agar (to isolate clones of bacteria cells “cloning” can also refer to the various means of creating cloned (“clonal”) organisms).

DNA can also be amplified using a procedure called the polymerase chain reaction (PCR).[92] By using specific short sequences of DNA, PCR can isolate and exponentially amplify a targeted region of DNA. Because it can amplify from extremely small amounts of DNA, PCR is also often used to detect the presence of specific DNA sequences.

DNA sequencing, one of the most fundamental technologies developed to study genetics, allows researchers to determine the sequence of nucleotides in DNA fragments. The technique of chain-termination sequencing, developed in 1977 by a team led by Frederick Sanger, is still routinely used to sequence DNA fragments.[93] Using this technology, researchers have been able to study the molecular sequences associated with many human diseases.

As sequencing has become less expensive, researchers have sequenced the genomes of many organisms using a process called genome assembly, which utilizes computational tools to stitch together sequences from many different fragments.[94] These technologies were used to sequence the human genome in the Human Genome Project completed in 2003.[34] New high-throughput sequencing technologies are dramatically lowering the cost of DNA sequencing, with many researchers hoping to bring the cost of resequencing a human genome down to a thousand dollars.[95]

Next-generation sequencing (or high-throughput sequencing) came about due to the ever-increasing demand for low-cost sequencing. These sequencing technologies allow the production of potentially millions of sequences concurrently.[96][97] The large amount of sequence data available has created the field of genomics, research that uses computational tools to search for and analyze patterns in the full genomes of organisms. Genomics can also be considered a subfield of bioinformatics, which uses computational approaches to analyze large sets of biological data. A common problem to these fields of research is how to manage and share data that deals with human subject and personally identifiable information. See also genomics data sharing.

On 19 March 2015, a group of leading biologists urged a worldwide ban on clinical use of methods, particularly the use of CRISPR and zinc finger, to edit the human genome in a way that can be inherited.[98][99][100][101] In April 2015, Chinese researchers reported results of basic research to edit the DNA of non-viable human embryos using CRISPR.[102][103]

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Genetics – Wikipedia

Genetic predisposition – Wikipedia

A genetic predisposition is a genetic characteristic which influences the possible phenotypic development of an individual organism within a species or population under the influence of environmental conditions. In medicine, genetic susceptibility to a disease refers to a genetic predisposition to a health problem,[1] which may eventually be triggered by particular environmental or lifestyle factors, such as tobacco smoking or diet. Genetic testing is able to identify individuals who are genetically predisposed to certain diseases.

Predisposition is the capacity we are born with to learn things such as language and concept of self. Negative environmental influences may block the predisposition (ability) we have to do some things. Behaviors displayed by animals can be influenced by genetic predispositions. Genetic predisposition towards certain human behaviors is scientifically investigated by attempts to identify patterns of human behavior that seem to be invariant over long periods of time and in very different cultures.

For example, philosopher Daniel Dennett has proposed that humans are genetically predisposed to have a theory of mind because there has been evolutionary selection for the human ability to adopt the intentional stance.[1] The intentional stance is a useful behavioral strategy by which humans assume that others have minds like their own. This assumption allows you to predict the behavior of others based on personal knowledge of what you would do.

In 1951, Hans Eysenck and Donald Prell published an experiment in which identical (monozygotic) and fraternal (dizygotic) twins, ages 11 and 12, were tested for neuroticism. It is described in detail in an article published in the Journal of Mental Science. in which Eysenck and Prell concluded that, “The factor of neuroticism is not a statistical artifact, but constitutes a biological unit which is inherited as a whole….neurotic Genetic predisposition is to a large extent hereditarily determined.”[2]

E. O. Wilson’s book on sociobiology and his book Consilience discuss the idea of genetic predisposition to behaviors

The field of evolutionary psychology explores the idea that certain behaviors have been selected for during the course of evolution.

The Genetic Information Nondiscrimination Act, which was signed into law by President Bush on May 21, 2008,[3] prohibits discrimination in employment and health insurance based on genetic information.

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Genetic predisposition – Wikipedia

Medical genetics – Wikipedia

Medical genetics is the branch of medicine that involves the diagnosis and management of hereditary disorders. Medical genetics differs from human genetics in that human genetics is a field of scientific research that may or may not apply to medicine, while medical genetics refers to the application of genetics to medical care. For example, research on the causes and inheritance of genetic disorders would be considered within both human genetics and medical genetics, while the diagnosis, management, and counselling people with genetic disorders would be considered part of medical genetics.

In contrast, the study of typically non-medical phenotypes such as the genetics of eye color would be considered part of human genetics, but not necessarily relevant to medical genetics (except in situations such as albinism). Genetic medicine is a newer term for medical genetics and incorporates areas such as gene therapy, personalized medicine, and the rapidly emerging new medical specialty, predictive medicine.

Medical genetics encompasses many different areas, including clinical practice of physicians, genetic counselors, and nutritionists, clinical diagnostic laboratory activities, and research into the causes and inheritance of genetic disorders. Examples of conditions that fall within the scope of medical genetics include birth defects and dysmorphology, mental retardation, autism, mitochondrial disorders, skeletal dysplasia, connective tissue disorders, cancer genetics, teratogens, and prenatal diagnosis. Medical genetics is increasingly becoming relevant to many common diseases. Overlaps with other medical specialties are beginning to emerge, as recent advances in genetics are revealing etiologies for neurologic, endocrine, cardiovascular, pulmonary, ophthalmologic, renal, psychiatric, and dermatologic conditions.

In some ways, many of the individual fields within medical genetics are hybrids between clinical care and research. This is due in part to recent advances in science and technology (for example, see the Human genome project) that have enabled an unprecedented understanding of genetic disorders.

Clinical genetics is the practice of clinical medicine with particular attention to hereditary disorders. Referrals are made to genetics clinics for a variety of reasons, including birth defects, developmental delay, autism, epilepsy, short stature, and many others. Examples of genetic syndromes that are commonly seen in the genetics clinic include chromosomal rearrangements, Down syndrome, DiGeorge syndrome (22q11.2 Deletion Syndrome), Fragile X syndrome, Marfan syndrome, Neurofibromatosis, Turner syndrome, and Williams syndrome.

In the United States, physicians who practice clinical genetics are accredited by the American Board of Medical Genetics and Genomics (ABMGG).[1] In order to become a board-certified practitioner of Clinical Genetics, a physician must complete a minimum of 24 months of training in a program accredited by the ABMGG. Individuals seeking acceptance into clinical genetics training programs must hold an M.D. or D.O. degree (or their equivalent) and have completed a minimum of 24 months of training in an ACGME-accredited residency program in internal medicine, pediatrics, obstetrics and gynecology, or other medical specialty.[2]

Metabolic (or biochemical) genetics involves the diagnosis and management of inborn errors of metabolism in which patients have enzymatic deficiencies that perturb biochemical pathways involved in metabolism of carbohydrates, amino acids, and lipids. Examples of metabolic disorders include galactosemia, glycogen storage disease, lysosomal storage disorders, metabolic acidosis, peroxisomal disorders, phenylketonuria, and urea cycle disorders.

Cytogenetics is the study of chromosomes and chromosome abnormalities. While cytogenetics historically relied on microscopy to analyze chromosomes, new molecular technologies such as array comparative genomic hybridization are now becoming widely used. Examples of chromosome abnormalities include aneuploidy, chromosomal rearrangements, and genomic deletion/duplication disorders.

Molecular genetics involves the discovery of and laboratory testing for DNA mutations that underlie many single gene disorders. Examples of single gene disorders include achondroplasia, cystic fibrosis, Duchenne muscular dystrophy, hereditary breast cancer (BRCA1/2), Huntington disease, Marfan syndrome, Noonan syndrome, and Rett syndrome. Molecular tests are also used in the diagnosis of syndromes involving epigenetic abnormalities, such as Angelman syndrome, Beckwith-Wiedemann syndrome, Prader-willi syndrome, and uniparental disomy.

Mitochondrial genetics concerns the diagnosis and management of mitochondrial disorders, which have a molecular basis but often result in biochemical abnormalities due to deficient energy production.

There exists some overlap between medical genetic diagnostic laboratories and molecular pathology.

Genetic counseling is the process of providing information about genetic conditions, diagnostic testing, and risks in other family members, within the framework of nondirective counseling. Genetic counselors are non-physician members of the medical genetics team who specialize in family risk assessment and counseling of patients regarding genetic disorders. The precise role of the genetic counselor varies somewhat depending on the disorder.

Although genetics has its roots back in the 19th century with the work of the Bohemian monk Gregor Mendel and other pioneering scientists, human genetics emerged later. It started to develop, albeit slowly, during the first half of the 20th century. Mendelian (single-gene) inheritance was studied in a number of important disorders such as albinism, brachydactyly (short fingers and toes), and hemophilia. Mathematical approaches were also devised and applied to human genetics. Population genetics was created.

Medical genetics was a late developer, emerging largely after the close of World War II (1945) when the eugenics movement had fallen into disrepute. The Nazi misuse of eugenics sounded its death knell. Shorn of eugenics, a scientific approach could be used and was applied to human and medical genetics. Medical genetics saw an increasingly rapid rise in the second half of the 20th century and continues in the 21st century.

The clinical setting in which patients are evaluated determines the scope of practice, diagnostic, and therapeutic interventions. For the purposes of general discussion, the typical encounters between patients and genetic practitioners may involve:

Each patient will undergo a diagnostic evaluation tailored to their own particular presenting signs and symptoms. The geneticist will establish a differential diagnosis and recommend appropriate testing. These tests might evaluate for chromosomal disorders, inborn errors of metabolism, or single gene disorders.

Chromosome studies are used in the general genetics clinic to determine a cause for developmental delay/mental retardation, birth defects, dysmorphic features, and/or autism. Chromosome analysis is also performed in the prenatal setting to determine whether a fetus is affected with aneuploidy or other chromosome rearrangements. Finally, chromosome abnormalities are often detected in cancer samples. A large number of different methods have been developed for chromosome analysis:

Biochemical studies are performed to screen for imbalances of metabolites in the bodily fluid, usually the blood (plasma/serum) or urine, but also in cerebrospinal fluid (CSF). Specific tests of enzyme function (either in leukocytes, skin fibroblasts, liver, or muscle) are also employed under certain circumstances. In the US, the newborn screen incorporates biochemical tests to screen for treatable conditions such as galactosemia and phenylketonuria (PKU). Patients suspected to have a metabolic condition might undergo the following tests:

Each cell of the body contains the hereditary information (DNA) wrapped up in structures called chromosomes. Since genetic syndromes are typically the result of alterations of the chromosomes or genes, there is no treatment currently available that can correct the genetic alterations in every cell of the body. Therefore, there is currently no “cure” for genetic disorders. However, for many genetic syndromes there is treatment available to manage the symptoms. In some cases, particularly inborn errors of metabolism, the mechanism of disease is well understood and offers the potential for dietary and medical management to prevent or reduce the long-term complications. In other cases, infusion therapy is used to replace the missing enzyme. Current research is actively seeking to use gene therapy or other new medications to treat specific genetic disorders.

In general, metabolic disorders arise from enzyme deficiencies that disrupt normal metabolic pathways. For instance, in the hypothetical example:

Compound “A” is metabolized to “B” by enzyme “X”, compound “B” is metabolized to “C” by enzyme “Y”, and compound “C” is metabolized to “D” by enzyme “Z”. If enzyme “Z” is missing, compound “D” will be missing, while compounds “A”, “B”, and “C” will build up. The pathogenesis of this particular condition could result from lack of compound “D”, if it is critical for some cellular function, or from toxicity due to excess “A”, “B”, and/or “C”. Treatment of the metabolic disorder could be achieved through dietary supplementation of compound “D” and dietary restriction of compounds “A”, “B”, and/or “C” or by treatment with a medication that promoted disposal of excess “A”, “B”, or “C”. Another approach that can be taken is enzyme replacement therapy, in which a patient is given an infusion of the missing enzyme.

Dietary restriction and supplementation are key measures taken in several well-known metabolic disorders, including galactosemia, phenylketonuria (PKU), maple syrup urine disease, organic acidurias and urea cycle disorders. Such restrictive diets can be difficult for the patient and family to maintain, and require close consultation with a nutritionist who has special experience in metabolic disorders. The composition of the diet will change depending on the caloric needs of the growing child and special attention is needed during a pregnancy if a woman is affected with one of these disorders.

Medical approaches include enhancement of residual enzyme activity (in cases where the enzyme is made but is not functioning properly), inhibition of other enzymes in the biochemical pathway to prevent buildup of a toxic compound, or diversion of a toxic compound to another form that can be excreted. Examples include the use of high doses of pyridoxine (vitamin B6) in some patients with homocystinuria to boost the activity of the residual cystathione synthase enzyme, administration of biotin to restore activity of several enzymes affected by deficiency of biotinidase, treatment with NTBC in Tyrosinemia to inhibit the production of succinylacetone which causes liver toxicity, and the use of sodium benzoate to decrease ammonia build-up in urea cycle disorders.

Certain lysosomal storage diseases are treated with infusions of a recombinant enzyme (produced in a laboratory), which can reduce the accumulation of the compounds in various tissues. Examples include Gaucher disease, Fabry disease, Mucopolysaccharidoses and Glycogen storage disease type II. Such treatments are limited by the ability of the enzyme to reach the affected areas (the blood brain barrier prevents enzyme from reaching the brain, for example), and can sometimes be associated with allergic reactions. The long-term clinical effectiveness of enzyme replacement therapies vary widely among different disorders.

There are a variety of career paths within the field of medical genetics, and naturally the training required for each area differs considerably. The information included in this section applies to the typical pathways in the United States and there may be differences in other countries. US practitioners in clinical, counseling, or diagnostic subspecialties generally obtain board certification through the American Board of Medical Genetics.

Genetic information provides a unique type of knowledge about an individual and his/her family, fundamentally different from a typically laboratory test that provides a “snapshot” of an individual’s health status. The unique status of genetic information and inherited disease has a number of ramifications with regard to ethical, legal, and societal concerns.

On 19 March 2015, scientists urged a worldwide ban on clinical use of methods, particularly the use of CRISPR and zinc finger, to edit the human genome in a way that can be inherited.[3][4][5][6] In April 2015 and April 2016, Chinese researchers reported results of basic research to edit the DNA of non-viable human embryos using CRISPR.[7][8][9] In February 2016, British scientists were given permission by regulators to genetically modify human embryos by using CRISPR and related techniques on condition that the embryos were destroyed within seven days.[10] In June 2016 the Dutch government was reported to be planning to follow suit with similar regulations which would specify a 14-day limit.[11]

The more empirical approach to human and medical genetics was formalized by the founding in 1948 of the American Society of Human Genetics. The Society first began annual meetings that year (1948) and its international counterpart, the International Congress of Human Genetics, has met every 5 years since its inception in 1956. The Society publishes the American Journal of Human Genetics on a monthly basis.

Medical genetics is now recognized as a distinct medical specialty in the U.S. with its own approved board (the American Board of Medical Genetics) and clinical specialty college (the American College of Medical Genetics). The College holds an annual scientific meeting, publishes a monthly journal, Genetics in Medicine, and issues position papers and clinical practice guidelines on a variety of topics relevant to human genetics.

The broad range of research in medical genetics reflects the overall scope of this field, including basic research on genetic inheritance and the human genome, mechanisms of genetic and metabolic disorders, translational research on new treatment modalities, and the impact of genetic testing

Basic research geneticists usually undertake research in universities, biotechnology firms and research institutes.

Sometimes the link between a disease and an unusual gene variant is more subtle. The genetic architecture of common diseases is an important factor in determining the extent to which patterns of genetic variation influence group differences in health outcomes.[12][13][14] According to the common disease/common variant hypothesis, common variants present in the ancestral population before the dispersal of modern humans from Africa play an important role in human diseases.[15] Genetic variants associated with Alzheimer disease, deep venous thrombosis, Crohn disease, and type 2 diabetes appear to adhere to this model.[16] However, the generality of the model has not yet been established and, in some cases, is in doubt.[13][17][18] Some diseases, such as many common cancers, appear not to be well described by the common disease/common variant model.[19]

Another possibility is that common diseases arise in part through the action of combinations of variants that are individually rare.[20][21] Most of the disease-associated alleles discovered to date have been rare, and rare variants are more likely than common variants to be differentially distributed among groups distinguished by ancestry.[19][22] However, groups could harbor different, though perhaps overlapping, sets of rare variants, which would reduce contrasts between groups in the incidence of the disease.

The number of variants contributing to a disease and the interactions among those variants also could influence the distribution of diseases among groups. The difficulty that has been encountered in finding contributory alleles for complex diseases and in replicating positive associations suggests that many complex diseases involve numerous variants rather than a moderate number of alleles, and the influence of any given variant may depend in critical ways on the genetic and environmental background.[17][23][24][25] If many alleles are required to increase susceptibility to a disease, the odds are low that the necessary combination of alleles would become concentrated in a particular group purely through drift.[26]

One area in which population categories can be important considerations in genetics research is in controlling for confounding between population substructure, environmental exposures, and health outcomes. Association studies can produce spurious results if cases and controls have differing allele frequencies for genes that are not related to the disease being studied,[27] although the magnitude of this problem in genetic association studies is subject to debate.[28][29] Various methods have been developed to detect and account for population substructure,[30][31] but these methods can be difficult to apply in practice.[32]

Population substructure also can be used to advantage in genetic association studies. For example, populations that represent recent mixtures of geographically separated ancestral groups can exhibit longer-range linkage disequilibrium between susceptibility alleles and genetic markers than is the case for other populations.[33][34][35][36] Genetic studies can use this admixture linkage disequilibrium to search for disease alleles with fewer markers than would be needed otherwise. Association studies also can take advantage of the contrasting experiences of racial or ethnic groups, including migrant groups, to search for interactions between particular alleles and environmental factors that might influence health.[37][38]

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Medical genetics – Wikipedia

Genetic Medicine – Imagenetics

Sanford Health has genetic counselors who are trained in both genetics and counseling. They are board certified and licensed. Genetic counseling helps people to understand the medical, psychological, and familial effects of genomics in a disease process.

Genetic counseling integrates the interpretation of family history, genomics, and medical history to assess the chance of having a disease or having a disease return as well as educate about inheritance, testing, management, prevention, resources, and research. A genetic counselor provides counseling to make informed choices and adjust to the risk or condition.

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Genetic Medicine – Imagenetics

Communication in genetic medicine – TGMI

Ive noticed over the last few weeks that many TGMI blog posts address challenges that specifically related to communication in genetic medicine. I wanted to highlight some of these mentions here, to illustrate that not all issues in genetic medicine are scientific or medical challenges. Sometimes its all about the way we share information with each other.

Looking back at recent blog posts, these are some of the communication challenges the TGMI team members noticed:

These are just some things that came up on the TGMI blog in the past few months, and while they look like very distinct problems, they are all about communication.

When clinicians and researchers need to use the same information, the requirements they have for how that information is presented can be very different

Of course an important point of communication is when patients need to understand the result of their genetic test and the implications of that result to a degree that allows them to make decisions about their own health. But communication isnt always about communication to patients or to a broader audience of non-experts. Even amongst themselves, researchers encounter communication challenges, with gene names being used inconsistently or inconsistent use of terms that articulate important issues such as the mode of inheritance, the risk of associated disease occurring, inconsistent methods used for annotating variations in genes and even many different ways of describing diseases or disorders and their consequences.

When clinicians and researchers need to use the same information, such as the link between a gene and a disease, the requirements they have for how that information is presented can be very different: Do they need it to understand genetics in general, or do they need it to very specifically understand the role genetic changes can have in one particular disease?

When two people talk to each other about genetics, they make assumptions about the level of genetic literacy the other person has. As Jennifer mentioned in last weeks blog post, the general level of genetic literacy has increased over the years. More people than before now know enough about genetics to talk about it in the context of a discussion about their health and hereditary conditions.

Still, this doesnt mean that all problems surrounding communication about genetics with non-experts have now been solved. For example, various studies have looked at communities where there is less awareness about genetic testing, or where a culture or language barrier affects communication. .

Were never going to get everyone at the same level of genetics knowledge, but that isnt necessary either. Genetically literate people dont need to know everything about genetics. They just need to have access to support and tools to help them find and understand relevant information and whats relevant is different for everyone. However it is important to improve the consistency in how different resources and tools use terms to describe genetic variation and the possible links those have to disease risk.

The same is true for communication between researchers and clinicians, or between researchers in different fields. They cant all be expected to know all the details of each others expertise, but they need to have a way to look up and extract the intended meaning from the information shared through publications, databases and other resources.

Last year, the American Heart Association published a statement to highlight this issue. They pointed out that researchers are rapidly finding new information about the link between genetics and cardiovascular disease, but that the clinician specialists who work with cardiovascular and stroke patients cant keep up with all this new genetics knowledge. The Association provided recommendations on how clinicians can acquire and maintain genetics competencies, and emphasised that clinicians not only need to have access to continued education about genetics, but also to tools and resources: The eventual goal is to empower and enable the cardiovascular clinician to understand, interpret, and apply genetic information to patient care in an effective, responsible, and cost-efficient manner.

These challenges arent unique to genetic medicine. Theyre all broad problems related to many areas of communication. Because these challenges are so ubiquitous, they are themselves the subject of academic study. Even just within science, there are fields such as Science of Team Science, which looks atcollaborations and effective communication between researchers, and Science of Science Communication, which studies how scientific information is disseminated to others.

Some studies look specifically at communication related to genetics and genomics. For example, how genetic literacy is measured, or how population sciences influence translational genomics.

The list at the top of this blog post only includes a few examples of communication challenges in genetic medicine, just enough to give you an idea of some of the different areas where communication is key. Id be curious to hear whether you have come across any other instances yourself either from your own experience or something youve heard or read about.

So, to turn this into two-way communication, please leave your thoughts in the comments below, or talk to us on Twitter. (Or you can always email us.)

Photo by Nik MacMillan on Unsplash

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Communication in genetic medicine – TGMI

Genetic Counseling – School of Medicine | University of …

What does it mean to be a genetic counseling student?

At the University of South Carolina it means you become part of the team from day one: an engaged learner in our genetics center.You’ll have an experienced primary faculty who are open door mentors in your preparation for this career.

You’ll have access in the classroom and in the clinic to the geneticist and genetic counselor faculty in our clinical rotation network of nine genetic centers. The world of genetic counseling will unfold for you in two very busy years, preparing you to take on the dozens of roles open to genetic counselors today.

Rigorous coursework, community service, challenging clinical rotations and a research-based thesis will provide opportunity for tremendous professional growth.

We’ve been perfecting our curriculum formore than 30 years to connect the knowledge with the skills youll need as a genetic counselor. Our reputation for excellence is known at home and abroad. We carefully review more than 140 applications per year to select the eight students who will graduate from the School of Medicine Genetic Counseling Program. Our alumni are our proudest accomplishment and work in the best genetic centers throughout the country. They build on our foundation to achieve goals in clinical care, education, research and industry beyond what we imagined.

First in the Southeast and tenth in the nation, we are one of 39 accredited programs in the United States. We have graduatedmore than 250 genetic counselors, many of whom are leading the profession today.

During your time with us you’ll get hands-on experience through a wide range of clinical opportunities in prenatal, pediatric and adult settings as well as specialty clinics. International rotations are encouraged through our partners in the Transnational Alliance for Genetic Counseling.

Weve received highly acclaimed Commendations for Excellence from the South Carolina Commission of Higher Education. American Board of Genetic Counseling accreditation was achieved in 2000, reaccreditation in 2006 and, most recently, theAccreditation Council for Genetic Counselingreaccreditation was awarded, 2014-2022.

You’ll have the chance to form lifelong partnerships with our core and clinical rotation faculty. You can begin to build your professional network with geneticists and genetic counselors throughout the Southeast and across the nation.

One of our program’s greatest assets is our alumni. This dedicated group regularly teaches and mentors our students,serves on our advisory board, raises money for our endowment and enjoys the instant connection when meeting other USC Genetic Counseling graduates. As a student, you’ll benefit from the network of connections these alumni are ready to offer you. Check out our Facebook group.

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Genetic Counseling – School of Medicine | University of …

Genetic predisposition – Wikipedia

A genetic predisposition is a genetic characteristic which influences the possible phenotypic development of an individual organism within a species or population under the influence of environmental conditions. In medicine, genetic susceptibility to a disease refers to a genetic predisposition to a health problem,[1] which may eventually be triggered by particular environmental or lifestyle factors, such as tobacco smoking or diet. Genetic testing is able to identify individuals who are genetically predisposed to certain diseases.

Predisposition is the capacity we are born with to learn things such as language and concept of self. Negative environmental influences may block the predisposition (ability) we have to do some things. Behaviors displayed by animals can be influenced by genetic predispositions. Genetic predisposition towards certain human behaviors is scientifically investigated by attempts to identify patterns of human behavior that seem to be invariant over long periods of time and in very different cultures.

For example, philosopher Daniel Dennett has proposed that humans are genetically predisposed to have a theory of mind because there has been evolutionary selection for the human ability to adopt the intentional stance.[1] The intentional stance is a useful behavioral strategy by which humans assume that others have minds like their own. This assumption allows you to predict the behavior of others based on personal knowledge of what you would do.

E. O. Wilson’s book on sociobiology and his book Consilience discuss the idea of genetic predisposition to behaviors

The field of evolutionary psychology explores the idea that certain behaviors have been selected for during the course of evolution.

The Genetic Information Nondiscrimination Act, which was signed into law by President Bush on May 21, 2008,[2] prohibits discrimination in employment and health insurance based on genetic information.

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Genetic predisposition – Wikipedia