The human mutation rate-how often new changes appear in the DNA-is fundamental to understanding many aspects of medical genetics and human evolutionary genetics.But it is low,and has therefore been difficult to measure.In the past,scientists could only estimate it approximately, either by observing how often mutant phenotypes appeared,or by comparison of humans and closely related species,such as chimpanzee, where many mutations could accumulate but the time period was uncertain.Now,a new study supported by the NSFC in China and The Royal Society in the UK reports the first direct measurement of the human mutation rate at the individual letters(nucleotides or bases) of DNA.This was possible because new(next)-generation sequencing technology is much more powerful than the methods available previously.The work was published in the leading journal Current Biology on 15th September 2009.The results were reported in the news by Nature, Science and the BBC,as well as in more than 20 Chinese newspapers and radio stations after the work first appeared online on 27th August.It was also one of the research highlights in Nature on 3rd September,which commented“This direct measurement of the human mutation rate should help researchers to refine evolutionary dating and better understand the source of genetic disease”.From the work,researchers could estimate that everyone has around 200 new mutations in their genome;as the authors said,“we are all mutants”.The ability to reliably measure rates of DNA mutation means we can begin to ask how mutation rates vary between different regions of the genome and perhaps also between different individuals.“,”The human mutation rate-how often new changes appear in the DNA-is fundamental to understanding many aspects of medical genetics and human evolutionary genetics.But it is low,and has therefore been difficult to measure.In the past,scientists could only estimate it approximately, either by observing how often mutant phenotypes appeared,or by comparison of humans and closely related species,such as chimpanzee, where many mutations could accumulate but the time period was uncertain.Now,a new study supported by the NSFC in China and The Royal Society in the UK reports the first direct measurement of the human mutation rate at the individual letters(nucleotides or bases) of DNA.This was possible because new(next)-generation sequencing technology is much more powerful than the methods available previously.The work was published in the leading journal Current Biology on 15th September 2009.The results were reported in the news by Nature, Science and the BBC,as well as in more than 20 Chinese newspapers and radio stations after the work first appeared online on 27th August.It was also one of the research highlights in Nature on 3rd September,which commented“This direct measurement of the human mutation rate should help researchers to refine evolutionary dating and better understand the source of genetic disease”.From the work,researchers could estimate that everyone has around 200 new mutations in their genome;as the authors said,“we are all mutants”.The ability to reliably measure rates of DNA mutation means we can begin to ask how mutation rates vary between different regions of the genome and perhaps also between different individuals.