Monthly Archives: June 2017

Researchers at the University of California, Davis, have just reported a small but significant accomplishment: catching the replication of a single DNA molecule on video for the first time. And the footage has revealed some surprising details about this structure on which all life depends.

DNA is composed of two strands bound together in a helical shape, like a twisting ladder. These strands are made of four basesadenine, guanine, cytosine and thymine, abbreviated as A, G, C and T, respectivelystrung together in various patterns and paired in specific ways across the rungs of the ladders. A always pairs with T, and C always pairs with G. Sugar and phosphate molecules help provide architectural support to the ladder-like structure. Human DNA contains about 3 billion bases. Discrete, repeated sequences of bases form the individual genes that encode the instructions for all our working parts. And every time a cell divides, which happens incredibly often, DNA replicates so that each new cell contains a complete copy of our entire genome, or genetic blueprint.

A digital representation of the human genome. Scientists at UC Davis have discovered that DNA replication is not as smooth as they thought. Mario Tama/Getty Images

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The process of DNA replication isa tremendous source of wonder and focus forresearch. The helix must unwind and have each strand copied smoothly and quickly. An enzyme called helicase triggers the unwinding and another called primase initiates the replication process. Athird, called polymerase, travels the length of a strand, adding the requisite base pairs along the way, leaving behind a new strand. Imagine splitting a ladder down the middle and assembling matching halves so that where there was once one ladder now there are two. That is DNA replication, only in place of saws, nails, wood and glue, there are enzymes and many microscopic and complex processes. Mysteries aboundwhen it comes to thishereditary material.

To better probe those mysteries, geneticist and microbiologist Stephen Kowalcyzkowski and colleagues watched DNA from bacteria replicate. They wanted to see exactly how fast the enzymes worked on each strand.

This first-ever view, shown in the video above, revealed a surprise: replication stopped unpredictably and moved at a varying pace. "The speed can vary about 10-fold," Kowalczykowski said in a statement. The two strands also replicated at different speeds.Sometimes the copying stalled on one strand while proceeding on the other. "We've shown that there is no coordination between the strands," said Kowalczykowski. "They are completely autonomous." The process, the researchers report in their study, published in Cell, is much more random than previously suspected.

The three enzymeshelicase, primase and polymeraseare also not alwys in sync. Even if polymerase stops its replication work, helicase can keep unzipping the helix. That lack of coordination leaves the half-helix of DNA exposed and vulnerable to damage. Such exposure is known to trigger repair mechanisms within the cell. Errors in replicating DNA, while often corrected, can also result ingenetic abnormalities that in turn lead to diseases.

This new look at DNA transforms the scientific understanding about replication. "It's a real paradigm shift," saidKowalcyzkowski, "and undermines a great deal of what's in the textbooks."

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DNA Replication Filmed for First Time Shows How Awkward and Random Genetics Is - Newsweek

A protein made by the fetus may lead to preeclampsia in moms.

People born to mothers who had the prenatal disorder were more likely to have certain DNA variationsnear a gene known to influence blood vessels. The results, published online June 19 in Nature Genetics, point to that gene as a possible preeclampsia culprit, and may help scientists develop ways to stop or prevent the pregnancy complication. Preeclampsia, which is marked by a dangerous spike in blood pressure, affects about 5 percent of pregnancies and is estimated to kill over 70,000 women a year globally.

Scientists have known that preeclampsia can run in families, but the genetics of the fetus hadnt been scrutinized. Over the years, people have looked at mothers genes, says geneticist Linda Morgan of the University of Nottingham in England. This is the first large study to look at babies genes.

Morgan and colleagues compared DNA variations in 2,658 babies, children and adults born to mothers who had preeclampsia with those in more than 300,000 people. (This large group probably included some people born to mothers with the condition, but the vast majority were not.)

A genome-wide association study (GWAS), a technique used to comb through DNA looking for genetic variations that may be linked to a disorder, pinpointed a spot on chromosome 13, near a gene called FLT1. That gene is involved with blood vessel formation, an intricate process for the placenta as it grows into the inside wall of the uterus and merges the babys blood supply to the mothers. The same genetic hot spot turned up in tests of a second group of offspring from mothers who had preeclampsia, Morgan and colleagues report. Another DNA variation near the gene also showed a link to the disorder.

Identifying FLT1 makes a lot of sense, says Ananth Karumanchi, a vascular biologist at Beth Israel Deaconess Medical Center in Boston, who was not involved in the study. Earlier experiments by Karumanchi and others suggest that the gene plays a role in preeclampsia.

Preeclampsia is kicked off by the placenta, an organ grown mostly from fetal cells that helps provide nutrients to the fetus. And though the details are unclear, some scientists suspect that unhealthy placentas start to pump out too much Flt-1 protein. A version of the protein called sFlt-1 can then slip into a mothers bloodstream, where it may damage blood vessels in a way that leads to high blood pressure.

The GWAS results cant explain the bulk of preeclampsia cases. A fetus carrying a single copy of one of the troublesome variants near FLT1 raised a mothers risk of preeclampsia by about 20 percent, the analysis suggests. Other risk factors are known to be much stronger, Morgan says, including previous high blood pressure, former preeclampsia diagnoses or carrying twins.

Karumanchi says that the genetic results might not be strong enough on their own to make the case that the gene is involved. But other work points to FLT1. We feel its the right target, he says.

In Europe, a preliminary clinical trial is testing a filtration method that removes excess sFlt-1 protein from the blood of women with signs of preeclampsia. So far, about 20 women have undergone the procedure, says nephrologist Ravi Thadhani of Massachusetts General Hospital in Boston. Early results are quite encouraging, he says, and he hopes to expand the study soon.

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A baby's DNA may kick off mom's preeclampsia - Science News Magazine

Long before cats became the darlings of Facebook and YouTube, they spread through the ancient human world.

A DNA study reached back thousands of years to track that conquest and found evidence of two major dispersals from the Middle East, in which people evidently took cats with them. Genetic signatures the felines had on those journeys are still seen in most modern-day breeds.

Researchers analyzed DNA from 209 ancient cats as old as 9,000 years from Europe, Africa and Asia, including some ancient Egyptian cat mummies.

They are direct witnesses of the situation in the past, said Eva-Maria Geigl of the Jacques Monod Institute in Paris. She and colleagues also looked at 28 modern feral cats from Bulgaria and east Africa.

Its the latest glimpse into the complicated story of domesticated cats. They are descendants of wild ancestors that learned to live with people and became relatively tame though some cat owners would say that nowadays, they dont always seem enthusiastic about our company.

The domestication process may have begun around 10,000 years ago when people settled in the Fertile Crescent, the arch-shaped region that includes the eastern shore of the Mediterranean Sea and land around the Tigris and Euphrates rivers. They stored grain, which drew rodents, which in turn attracted wild cats. Animal remains in trash heaps might have attracted them too. Over time, these wild felines adapted to this man-made environment and got used to hanging around people.

Previous study had found a cat buried alongside a human some 9,500 years ago in Cyprus, an island without any native population of felines. That indicates the cat was brought by boat and it had some special relationship to that person, researchers say.

Cats were clearly tame by about 3,500 years ago in Egypt, where paintings often placed them beneath chairs. That shows by that time, the cat makes its way to the household, said Geigl.

But the overall domestication process has been hard for scientists to track, in part because fossils skeletons dont reveal whether a cat was wild or domesticated.

Its easier to distinguish dogs, our first domesticated animal, from their wolf ancestors. Dogs evolved from wolves that had begun to associate with people even before farming began, perhaps drawn by the food the humans left behind.

The new study tracked the spread of specific cat DNA markers over long distances through time, a sign that people had taken cats with them. Results were released Monday by the journal Nature Ecology & Evolution.

The study strengthens and refines previous work, said Carlos Driscoll of the Wildlife Institute of India. The extensive sampling of cat DNA going back so far in time is unprecedented, he said.

Researchers also looked for a genetic variant that produces the blotchy coat pattern typical of modern-day domestic cats, rather than the tiger-like stripes seen in their wild cousins. It showed up more often in samples from after the year 1300 than earlier ones, which fits with other evidence that the tabby cat markings became common by the 1700s and that people started breeding cats for their appearance in the 1800s.

Thats late in the domestication of cats, in contrast to horses, which were bred for their appearance early on, Geigl said.

Most of the study focused on the ancient dispersals of cats. In the DNA samples analyzed, one genetic signature found first in the Asian portion of Turkey and perhaps once carried by some Fertile Crescent cats showed up more than 6,000 years ago in Bulgaria.

That indicates cats had been taken there by boat with the first farmers colonizing Europe, Geigl said. It also appeared more than 5,000 years ago in Romania, as well as around 3,000 years ago in Greece.

A second genetic signature, first seen in Egypt, had reached Europe between the first and fifth centuries, as shown by a sample from Bulgaria. It was found in a seventh-century sample from a Viking trading port in northern Europe, and an eighth-century sample from Iran.

The dispersal of the cats across the Mediterranean was probably encouraged by their usefulness in controlling rodents and other pests on ships, the researchers said.

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DNA study reveals cats traveled with humans centuries ago - New York Post

A lost hat while fleeing police led to a DNA match and an arrest in a burglary attempt at a local storage facility.

Matthew Kelly Carpenter, 34, was allegedly caught in the act by law enforcement at the storage facility on South Cherokee Street in Muskogee in late January, according to the probable cause affidavit filed in the case Wednesday.

Carpenter fled officers, losing his hat in the progress. DNA from the hat was sent to the Oklahoma State Bureau of Investigation for testing, and it came back as a match to Carpenter, the court documents state.

He has two prior convictions of second-degree burglary, according to supplemental information filed with the charges.

Carpenter was arrested Tuesday and is held without bond on four charges of second-degree burglary and two charges of attempted second-degree burglary, according to court documents.He returns to court June 26.

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Alleged burglar identified through DNA - Muskogee Daily Phoenix