An international team of scientists has managed to make the first direct measurement of the overall rate of genetic mutation in humans. The results - published in the journal Current Biology - and the method developed by the researchers provide a better understanding of the mutation rates and reduced, in line with the objectives of the scientists, mutations. According to British scientists and Chinese, the mutation is the basis of genetic variation that determines the onset of certain diseases - like cancer - and is a molecular clock that allows you to assess the evolutionary time scale. The improvement of knowledge about mutation rates would help to strengthen medical research and to shed light on human evolution and optimization of the measurements of the rate of mutation would also enable a more effective regulation of the clock of evolution. In the past, estimates of the mutation rate was obtained from phenotypic observations or by comparing sequences of similar species related. In this latest research, scientists have carried out the sequencing of the same stretch of DNA (more than 10 million "letters", or of nucleotides belonging to the Y chromosome) by two Chinese men separated by 13 generations and counted the differences. The men involved in this study belonged to a family that for centuries lived in the same village and whose common ancestor lived more than two hundred years ago. The researchers found that the Y chromosome is rarely subject to mutation and that it is transmitted unchanged from father to son. Over the generations the mutations occurred very slowly. The research team identified 12 mutations, 8 of which occurred in vitro and 4 of which occurred in vivo, or in a natural way from generation to generation. According to held by members of the team 10,149,073 10,149,085 letters examined were identical. "These four mutations have allowed us to calculate accurately the mutation rate: 1 out of 30 million nucleotides per generation. The result confirmed the expectations," said Dr Chris Tyler-Smith of The Wellcome Trust Sanger Institute, head of the project. "The results are reassuring because the methods we used, taking advantage of new sequencing technology, had not yet been used for this type of research. There are many genetic diseases result from new mutations," he added. "The accurate assessment of DNA mutations we can now begin to ask how the mutation rates vary between different regions of the genome and perhaps even between different individuals. "Humans are a number of new mutations in the DNA that varies from 100 to 200 (single base changes in DNA sequence that differ from the sequence inherited from parents) have the researchers said, noting that this figure is equivalent to a mutation every 15-30 million nucleotides. Keep in mind that most of these mutations have no harmful consequences and that neither health nor physical appearance. "Until a few years ago would been impossible to imagine such a large amount of collected data, "said Dr. Yali Xue of The Wellcome Trust Sanger Institute (UK), first author of the study." Being able to identify so few of the mutations was an undertaking as complex as finding a needle in a haystack. "
Federico Cesareo
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