New DNA sequencing data reinforce the notion that the X and Y chromosomes, which determine biological sex in mammals, are locked in an evolutionary battle for supremacy.
David Page, a biologist who directs the Whitehead Institute in Cambridge, Massachusetts, and his colleagues explored the Y chromosomes carried by males of several species, mapping stretches of mysterious, repetitive DNA in unprecedented detail. These stretches may signal a longstanding clash of the chromosomes.
“This idea of conflict between the chromosomes has been around for a while,” says Tony Gamble, an evolutionary biologist at the University of Minnesota in Minneapolis. But the sequencing data from the bull’s Y chromosome suggests that the phenomenon is more widespread than previously thought, he adds.
The mammalian Y chromosome has long been thought of as a sort of genomic wasteland, usually shrinking over the course of evolution and largely bereft of pertinent information. Page’s work has helped to change perceptions of the Y chromosome by revealing that it contains remarkable patterns of repeating sequences that appear dozens to hundreds of times.
Page argues that his findings are evidence that the genes are involved in meiotic drive, a somewhat mysterious biological process that subverts the standard rules of heredity. In it, a particular version of a gene — or in this case, an entire chromosome — manages to increase the frequency by which it is transmitted to the next generation.
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