Human genetics is the study of inheritance as it occurs in human beings. Human genetics encompasses a variety of overlapping fields including: classical genetics, cytogenetics, molecular genetics, biochemical genetics, genomics, population genetics, developmental genetics, clinical genetics, and genetic counseling.
Genes can be the common factor of the qualities of most human-inherited traits. Study of human genetics can be useful as it can answer questions about human nature, understand the diseases and development of effective disease treatment, and understand genetics of human life. This article describes only basic features of human genetics; for the genetics of disorders please see: medical genetics.
Inheritance of traits for humans are based upon Gregor Mendel's model of inheritance. Mendel deduced that inheritance depends upon discrete units of inheritance, called factors or genes.
Autosomal traits are associated with a single gene on an autosome (non-sex chromosome)they are called "dominant" because a single copyinherited from either parentis enough to cause this trait to appear. This often means that one of the parents must also have the same trait, unless it has arisen due to an unlikely new mutation. Examples of autosomal dominant traits and disorders are Huntington's disease and achondroplasia.
Autosomal recessive traits is one pattern of inheritance for a trait, disease, or disorder to be passed on through families. For a recessive trait or disease to be displayed two copies of the trait or disorder needs to be presented. The trait or gene will be located on a non-sex chromosome. Because it takes two copies of a trait to display a trait, many people can unknowingly be carriers of a disease. From an evolutionary perspective, a recessive disease or trait can remain hidden for several generations before displaying the phenotype. Examples of autosomal recessive disorders are albinism, cystic fibrosis.
X-linked genes are found on the sex X chromosome. X-linked genes just like autosomal genes have both dominant and recessive types. Recessive X-linked disorders are rarely seen in females and usually only affect males. This is because males inherit their X chromosome and all X-linked genes will be inherited from the maternal side. Fathers only pass on their Y chromosome to their sons, so no X-linked traits will be inherited from father to son. Men cannot be carriers for recessive X linked traits, as they only have one X chromosome, so any X linked trait inherited from the mother will show up.
Females express X-linked disorders when they are homozygous for the disorder and become carriers when they are heterozygous. X-linked dominant inheritance will show the same phenotype as a heterozygote and homozygote. Just like X-linked inheritance, there will be a lack of male-to-male inheritance, which makes it distinguishable from autosomal traits. One example of an X-linked trait is CoffinLowry syndrome, which is caused by a mutation in ribosomal protein gene. This mutation results in skeletal, craniofacial abnormalities, mental retardation, and short stature.
X chromosomes in females undergo a process known as X inactivation. X inactivation is when one of the two X chromosomes in females is almost completely inactivated. It is important that this process occurs otherwise a woman would produce twice the amount of normal X chromosome proteins. The mechanism for X inactivation will occur during the embryonic stage. For people with disorders like trisomy X, where the genotype has three X chromosomes, X-inactivation will inactivate all X chromosomes until there is only one X chromosome active. Males with Klinefelter syndrome, who have an extra X chromosome, will also undergo X inactivation to have only one completely active X chromosome.
Y-linked inheritance occurs when a gene, trait, or disorder is transferred through the Y chromosome. Since Y chromosomes can only be found in males, Y linked traits are only passed on from father to son. The testis determining factor, which is located on the Y chromosome, determines the maleness of individuals. Besides the maleness inherited in the Y-chromosome there are no other found Y-linked characteristics.
A pedigree is a diagram showing the ancestral relationships and transmission of genetic traits over several generations in a family. Square symbols are almost always used to represent males, whilst circles are used for females. Pedigrees are used to help detect many different genetic diseases. A pedigree can also be used to help determine the chances for a parent to produce an offspring with a specific trait.
Four different traits can be identified by pedigree chart analysis: autosomal dominant, autosomal recessive, x-linked, or y-linked. Partial penetrance can be shown and calculated from pedigrees. Penetrance is the percentage expressed frequency with which individuals of a given genotype manifest at least some degree of a specific mutant phenotype associated with a trait.
Inbreeding, or mating between closely related organisms, can clearly be seen on pedigree charts. Pedigree charts of royal families often have a high degree of inbreeding, because it was customary and preferable for royalty to marry another member of royalty. Genetic counselors commonly use pedigrees to help couples determine if the parents will be able to produce healthy children.
A karyotype is a very useful tool in cytogenetics. A karyotype is picture of all the chromosomes in the metaphase stage arranged according to length and centromere position. A karyotype can also be useful in clinical genetics, due to its ability to diagnose genetic disorders. On a normal karyotype, aneuploidy can be detected by clearly being able to observe any missing or extra chromosomes.
Giemsa banding, g-banding, of the karyotype can be used to detect deletions, insertions, duplications, inversions, and translocations. G-banding will stain the chromosomes with light and dark bands unique to each chromosome. A FISH, fluorescent in situ hybridization, can be used to observe deletions, insertions, and translocations. FISH uses fluorescent probes to bind to specific sequences of the chromosomes that will cause the chromosomes to fluoresce a unique color.
Genomics refers to the field of genetics concerned with structural and functional studies of the genome. A genome is all the DNA contained within an organism or a cell including nuclear and mitochondrial DNA. The human genome is the total collection of genes in a human being contained in the human chromosome, composed of over three billion nucleotides. In April 2003, the Human Genome Project was able to sequence all the DNA in the human genome, and to discover that the human genome was composed of around 20,000 protein coding genes.
Medical genetics is the branch of medicine that involves the diagnosis and management of hereditary disorders. Medical genetics is the application of genetics to medical care. It overlaps human genetics, 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 counseling of individuals with genetic disorders would be considered part of medical genetics.
Population genetics is the branch of evolutionary biology responsible for investigating processes that cause changes in allele and genotype frequencies in populations based upon Mendelian inheritance. Four different forces can influence the frequencies: natural selection, mutation, gene flow (migration), and genetic drift. A population can be defined as a group of interbreeding individuals and their offspring. For human genetics the populations will consist only of the human species. The Hardy-Weinberg principle is a widely used principle to determine allelic and genotype frequencies.
In addition to nuclear DNA, humans (like almost all eukaryotes) have mitochondrial DNA. Mitochondria, the "power houses" of a cell, have their own DNA. Mitochondria are inherited from one's mother, and their DNA is frequently used to trace maternal lines of descent (see mitochondrial Eve). Mitochondrial DNA is only 16kb in length and encodes for 62 genes.
The XY sex-determination system is the sex-determination system found in humans, most other mammals, some insects (Drosophila), and some plants (Ginkgo). In this system, the sex of an individual is determined by a pair of sex chromosomes (gonosomes). Females have two of the same kind of sex chromosome (XX), and are called the homogametic sex. Males have two distinct sex chromosomes (XY), and are called the heterogametic sex.
Sex linkage is the phenotypic expression of an allele related to the chromosomal sex of the individual. This mode of inheritance is in contrast to the inheritance of traits on autosomal chromosomes, where both sexes have the same probability of inheritance. Since humans have many more genes on the X than the Y, there are many more X-linked traits than Y-linked traits.However, females carry two or more copies of the X chromosome, resulting in a potentially toxic dose of X-linked genes.
To correct this imbalance, mammalian females have evolved a unique mechanism of dosage compensation. In particular, by way of the process called X-chromosome inactivation (XCI), female mammals transcriptionally silence one of their two Xs in a complex and highly coordinated manner.
Here is the original post:
- Scientist Who Discovered BRCA1 Gene to Give Free Talk on Cancer And Genetics - Noozhawk - January 19th, 2020
- Genetic testing firm 23andMe is first to create a drug using its customers' DNA - The Times - January 19th, 2020
- Hackensack Meridian Health Center for Discovery and Innovation to Host Genomic Medicine Symposium - P&T Community - January 19th, 2020
- 11 Year-Old Bertrand Might Cant Cry Scientists Have Now Discovered Why - SciTechDaily - January 19th, 2020
- Transposons Identified as Likely Cause of Undiagnosed Diseases - The Scientist - January 19th, 2020
- Do genetic ancestry tests know if you're Palestinian? A cautionary tale of race and science - ABC News - January 19th, 2020
- Controlling Our Own Evolution: What is the Future of Gene-Editing? - The Globe Post - January 19th, 2020
- There is a new player in adult bone healing - Baylor College of Medicine News - January 19th, 2020
- Air Pollution, Evolution, and the Fate of Billions of Humans - The New York Times - January 19th, 2020
- A New York Times column on 'Jewish genius' draws criticism for linking to a debunked University of Utah study - Salt Lake Tribune - January 5th, 2020
- Ambroxol Reverses Bone Damage in Girl With GD Type 1, Case Study Shows - Gaucher Disease News - January 5th, 2020
- Gene editing breakthroughs that cured genetic diseases in 2019 - The Star Online - January 5th, 2020
- Digid8 and the Emergence of DNA Matchmaking - Study Breaks - January 5th, 2020
- Etched in DNA: Decoding the secrets of the past - Christian Science Monitor - January 5th, 2020
- The Face of Science - Clemson World magazine - January 5th, 2020
- Aborting Babies Because They're Gay: Coming Soon to China - Patheos - January 5th, 2020
- Mutants among us: "Natural short sleepers" reveal the genetics of sleep - Inverse - January 5th, 2020
- The End of Infertility Is in Sight - UCSF News Services - January 5th, 2020
- Who is a Jew? DNA home testing adds new wrinkle to age-old debate - The Jewish News of Northern California - December 1st, 2019
- Humans and autoimmune diseases continue to evolve together - Medical News Today - December 1st, 2019
- Mutations in emerging autism gene tied to distinct traits - Spectrum - December 1st, 2019
- Gail Fisher's 'Dog Tracks': Spoiling you dog with extra food could cut short its life - The Union Leader - December 1st, 2019
- In a Wisconsin village, the doctor makes house calls and sees the rarest diseases on Earth - USA TODAY - December 1st, 2019
- Alzheimer's and Autism: Researchers Pinpoint Genetic Mutations Overlapping in Both Diseases - Being Patient - December 1st, 2019
- How do consumer DNA tests from the US and China stack up? - Abacus - December 1st, 2019
- Is Nature vs. Nurture an Outdated Concept? - The National Interest Online - December 1st, 2019
- Collection of genetic data leads to privacy concerns - The New Economy - December 1st, 2019
- Is sexual orientation genetic? Yes and no, an extensive study finds - Haaretz - November 19th, 2019
- Sexual orientation cannot be changed at will, lawyers argue - The Straits Times - November 19th, 2019
- Adam and Eve Are Possible: A Second Bite at the Genetic Apple - Christianheadlines.com - November 19th, 2019
- InterVenn Biosciences Announces Positive Interim Clinical Trial Results and Appoints Biotech Veteran Klaus Lindpaintner, M.D. as Chief Scientific and... - November 19th, 2019
- How maternal Zika infection results in newborn microcephaly - Baylor College of Medicine News - November 19th, 2019
- Dicerna scores broad, 'rest of liver' deal with Novo Nordisk, bagging $225M in cash to hit some 30 targets with RNAi platform - Endpoints News - November 19th, 2019
- Sexual orientation cannot be wilfully changed, say lawyers fighting to repeal Section 377A - The Straits Times - November 19th, 2019
- The American Heart Association's Annual Conference Comes to Philly This Weekend - Philadelphia magazine - November 19th, 2019
- Clear link between genetics and depressive symptoms uncovered - The Age - November 19th, 2019
- At-Home DNA Tests Still Need the 'Human Touch,' Say Panelists at Genomics Roundtable Workshop - National Academies of Sciences, Engineering, and... - November 19th, 2019
- How in utero Zika virus infection can lead to microcephaly in newborns: Baylor research - Outbreak News Today - November 19th, 2019
- Taller People have Increased Risk of Irregular Heartbeat - News18 - November 19th, 2019
- In Down syndrome mouse model, scientists reverse intellectual deficits with drugs - University of California - November 19th, 2019
- Alector Reports Recent Business Highlights and Third Quarter 2019 Financial Results - GlobeNewswire - November 19th, 2019
- One of the World's Greatest Geneticists, He Gave Up British Citizenship for India - The Better India - November 19th, 2019
- Section 377A constitutional challenge: Expert evidence reveal sexual orientation cannot be changed at will, lawyers argue - The Online Citizen - November 19th, 2019
- Co-creator of CRISPR lectures about future applications of genome editing technology - Daily Bruin - November 19th, 2019
- Connecting gene mutations, rare genetic diseases - Baylor College of Medicine News - October 28th, 2019
- Utah researchers discover link between certain brain cells and anxiety, OCD - KSL.com - October 28th, 2019
- UH Receives $2M to Study Cancer Risks of Environmental Toxins - Big Island Now - October 28th, 2019
- Genetic testing could keep you healthy. But what about personal info? - Deseret News - October 28th, 2019
- Student group works to foster diversity in the sciences - UChicago News - October 28th, 2019
- Takeaways from ASHG 2019 in Houston: Users of Bionano's Saphyr System Presented Validation Results for FSHD, Repeat Expansion Disorders and Digital... - October 28th, 2019
- DNA research holds the keys to human history but it's being weaponized by politicians - Haaretz - October 28th, 2019
- Scientists have created the first-ever 18-carbon ring, a major feat of molecular architecture - Massive Science - October 28th, 2019
- Law, Privacy and Genome Human Rights Failure in Russia - Putin's Fascination with Hitler's Eugenics Project - Communal News - October 28th, 2019
- Neural activity plays an important role in longevity - CMU The Tartan Online - October 28th, 2019
- Book Summary: Genetics and the Aryan Debate by Shrikant Talageri- I - IndiaFacts - October 28th, 2019
- Cryptocurrency News: This Week on Bitfinex, Tether, Coinbase, & More - May 25th, 2019
- Ripple Price Forecast: XRP vs SWIFT, SEC Updates, and More - May 25th, 2019
- Cryptocurrency News: Bitcoin ETFs, Andreessen Horowitz, and Contradictions in Crypto - May 25th, 2019
- Cryptocurrency News: Looking Past the Bithumb Crypto Hack - May 25th, 2019
- Cryptocurrency News: XRP Validators, Malta, and Practical Tokens - May 25th, 2019
- Cryptocurrency News: Bitcoin ETF Rejection, AMD Microchip Sales, and Hedge Funds - May 25th, 2019
- Cryptocurrency News: What You Need to Know This Week - May 25th, 2019
- Bitcoin Rise: Is the Recent Bitcoin Price Surge a Sign of Things to Come or Another Misdirection? - May 25th, 2019
- Cryptocurrency News: Vitalik Buterin Doesn’t Care About Bitcoin ETFs - May 25th, 2019
- Cryptocurrency News: New Exchanges Could Boost Crypto Liquidity - May 25th, 2019
- Human Genetics - medschool.ucla.edu - May 5th, 2019
- Department of Human Genetics | The University of Chicago - May 5th, 2019
- Human genetics | biology | Britannica.com - May 2nd, 2019
- What is Bitcoin Cash? - finance.yahoo.com - April 29th, 2019
- Bitcoin Soars As Ethereum, Ripple's XRP, Bitcoin Cash, And ... - April 29th, 2019
- Bitcoin Cash - finance.yahoo.com - April 29th, 2019
- What is Bitcoin Cash? - Coin Rivet - April 29th, 2019
- Bitcoin Cash - Wikipedia - April 29th, 2019
- Ripple Price Forecast: XRP vs SWIFT, SEC Updates, and More - April 21st, 2019
- Cryptocurrency News: Looking Past the Bithumb Crypto Hack - April 21st, 2019
- Cryptocurrency News: This Week on Bitfinex, Tether, Coinbase, & More - April 21st, 2019
- Cryptocurrency News: XRP Validators, Malta, and Practical Tokens - April 21st, 2019
- Cryptocurrency News: Bitcoin ETFs, Andreessen Horowitz, and Contradictions in Crypto - April 21st, 2019
- Cryptocurrency News: New Exchanges Could Boost Crypto Liquidity - April 21st, 2019
- Cryptocurrency News: Bitcoin ETF Rejection, AMD Microchip Sales, and Hedge Funds - April 21st, 2019