EVOLUTION: Y FILES CLOSER TO THE X
In 1947, the biologist J. B. S. Haldane suggested that the rate of genetic mutation is much higher in the male than in the female germ line. This idea has received support from studies in primates generally indicating that mutations occur five times as often in the male than in the female germline.
This ratio is revised sharply downwards - to around 1.7 - in a report in Nature [Vol. 406, Issue 6796 (2000), pp. 622-625] from David C. Page and colleagues from the Howard Hughes Medical Institute at the Whitehead Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts.
This finding has implications for medical genetics, in particular the analysis of sex-linked genetic disorders that are inherited more from the father than the mother.
The researchers' estimate of the relative mutation rate is unprecedentedly accurate, as it is based on a comparison between very large regions of the X and Y chromosomes that contain few genes. So this estimate is unlikely to have been biased by natural selection. In an added twist, the regions compared are around 99% identical: the region on the Y chromosome is a version of part of the X chromosome that was copied and transposed three or four million years ago, early in human evolution. This X-to-Y translocation is not found in chimpanzees or gorillas. This finding allows the rate of subsequent sequence divergence to be calibrated with reference to a known event in humanity's past.
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(C) Nature press release.
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