Scientists explain why the rate of change is difficult to determine the genome.

Recently, the mutation rate in humans conference held in Leipzig, Germany, 12 speakers expressed themselves in trying to think why in recent years related to the calculation of the rate of decrease than in the past. They also seem to ponder why the rate fluctuates over time.

Scientists explain why the rate of change is difficult to determine the genome

Human gene mutation is not only described as a science fiction movie, they can record the time evolution of the event. Source: Murray Close / Getty

 

Mathematicians have been calculating π values, even if they already know more than 12 trillion figure; physicists are constantly remind ourselves, because they can not determine the gravitational constant three significant figures outside. In contrast, a geneticist at the speed of human DNA mutations are facing a dilemma.

The rate for correction “molecular clock” is very important. DNA molecular clock dates of events can be placed in the evolutionary history. Recently, the mutation rate in humans conference held in Leipzig, Germany, 12 speakers expressed themselves in trying to think why in recent years related to the calculation of the rate of decrease than in the past. They also seem to ponder why the rate fluctuates over time. The meeting attracted not only evolutionary geneticist, also attracted interest in cancer and reproductive biology researchers note.

“Change is the ultimate source of all genetic diseases and biological adaptation, so understanding the mutation rate of development is a fundamental problem.” The experts, human geneticist at Columbia University, said Molly Przeworski.

Even before the known DNA encoding genetic information, researchers have tried to implant a number of human mutation rate. In the 1930s, genetics pioneer JBS Haldane made a good assessment methods, how to measure the impact of hemophilia mutation in a large family of incidence.

After mutation rate estimate was calculated to extend DNA and amino acid sequences of different proteins in humans and chimpanzees and other apes, and then follow the time of occurrence of these species in the fossil record of the most recent common ancestor divide the number of differences.However, the incomplete fossil record greatly influenced the results of these calculations, the researchers finally agreed: on average, each DNA letter mutation in every 10 billion years. Max Planck Institute molecular anthropologist Linda Vigilant said it was a “suspicious integer.”

In the past six years, more direct measurements using a “next generation” DNA sequencing technology, the result of a very different conclusion. Many studies have compared the entire genomes of parents and their offspring, the result of the mutation rate is about half of the common ancestor of the method.

A slower molecular clocks can well coordinate the results of genetic and archaeological important events in human evolution, such as Out of Africa. But when further back in time, using a slow clock conclusion does not make sense, such as apes and monkeys recent common ancestor of dinosaurs ever met. Many researchers reluctant to give up the old data, the start of betting on both sides in the paper to avoid losses, in accordance with the mutation rate fast, slow, or living in between, for the evolutionary events provides multiple data.

Last year, Harvard Medical School geneticist David Reich of mankind and his colleagues, the 45 000 years ago in Siberia and modern human genomes were compared, the result of a slower rate. Just before the meeting Leipzig (Kay Prüfer the conference jointly organized by the Reich and the Max Planck Society), Reich research team published a paper preprints, by focusing on the differences between the modern extension of the paired chromosomes, reached a centered conclusions. But Reich and was unable to explain this contradiction. “Molecular clock so uncertain facts are very problematic for us.” He said, “This means that the date is very inferior genetics and uncertain.”

Reich hope, even if the meeting could not reach a consensus on the mutation rate, but also to emphasize that the research needs to move forward. He and Prüfer organizational participants endorsed the theory of voting. They found that participants agreed with a lower value better, but still a very wide range of opinions.

Reich et al concluded that the human mutation rates have fluctuated over the past millions of years.Many discussions were around when accelerating and decelerating what it is and why. The metabolic aspects of reproductive biology and evolutionary change are likely to be the cause. Cambridge University population geneticist Aylwyn Scally believes that living in 20 million years ago – 12 million years ago, the common ancestor of apes, monkeys have a longer than its relatives generations. This may slow down the mutations: a longer annual generation may result in fewer mutations.

Medical aspects of geneticists also worried mutation rate. British participation in the conference Wellcome Trust Sanger Institute Michael Stratton is a cancer geneticist working on the causes DNA mutations. Stratton said tobacco and other environmental factors can trigger a number of cancers, but ordinary biochemical processes can also cause cancer cells. These factors can explain or identify the mutation rate fluctuations.

Reproductive biologists interested in the human mutation rate, partly because they found a number of diseases in children older fathers are more common. Men produce sperm throughout a lifetime, but women are born with all the eggs. Sperm precursor cells fixed division means that men will be more new mutations passed on to offspring, the 2012 survey, this probability is four times higher than women, and older and father passed mutations more .

Even if the human gene mutation rate is still uncertain and unstable, Reich researchers proposed the use of a slower rate in the study, at least until better data appears. He warned: “This is not the speed of light, not physics.”

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