11 September 2009
Y chromosome not such a dud
by Kate Melville
It was believed that the X and Y chromosomes - that define the sexes - did not communicate at all, but UK researchers from the University of Leicester's Department of Genetics have shown that exchanges of DNA do occur between the X and Y in the regions previously thought to be completely isolated.
Recently, it was shown that the Y chromosome can talk to itself - swapping bits of DNA from one region to another, and potentially giving it a way to fix mutations that might affect male fertility. "In this new research we've now shown that it actually maintains a genetic conversation with the X chromosome, potentially giving it a way to fix other kinds of mutations, too. So, maybe it's not quite the dysfunctional loner we have always imagined it to be," said Professor Mark Jobling, who led the study.
The study, published in the American Journal of Human Genetics may cause some scientists to reassess their prediction of the Y chromosome's eventual demise. "These days the X and Y are a very odd couple, but long ago, before mammals evolved, they were an ordinary pair of identical chromosomes, exchanging DNA in a companionable way through the process of genetic recombination. However, once the Y chromosome took on the job of determining maleness, they stopped talking to each other. The X remained much the same, but the Y set out on a path of degeneration that saw it lose many of its genes and shrink to about one third the size of the X," explained Jobling.
Interestingly, the researchers discovered that the "conversation" between the X and Y chromosome goes both ways, and mutations arising on a decaying Y chromosome can be passed to the X. "Perhaps that's the Y chromosome's revenge," suggests Jobling. He added that future work will assess how widespread X-Y exchanges have been during evolution, and what the likely functional effects might be.
Source: University of Leicester