Male Y chromosome not as rare as first thought

By Steve Connor

Reports of the demise of the male Y chromosome have been greatly exaggerated, scientists say.
Photo / Thinkstock
Reports of the demise of the male Y chromosome have been greatly exaggerated, scientists say. Photo / Thinkstock

New research manages to soothe mens fears about becoming surplus to requirements.

Gentlemen, stand at ease. Reports of the demise of the male Y chromosome have been greatly exaggerated, according to scientists who believe men are not in danger of their predicted extinction.

Two independent studies of the diminutive Y chromosome, which is inherited solely down the male line, have failed to find evidence to support the widely held theory that its evolutionary days and those of its owners are numbered.

A detailed genetic analysis of the Y chromosomes of a wide range of mammalian species, including humans, shows that far from continuing to wither away unremittingly, it has remained remarkably stable for at least the past 25 million years.

The research also found that the few remaining genes on the Y chromosome include some that perform vital regulatory control of other genes that are active throughout a mans body making each of his cells distinctly and subtly different from those of a woman.

This would suggest that medical treatments should in future be tailored more towards a patients gender and that doctors may have more reason to treat men and women differently according to their sex, said Professor David Page, director of the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts.

We need to move beyond a unisex model of our understanding and treatment of disease, said Professor Page, who led one of the research teams. Henrik Kaessmann of the University of Lausanne, who led the second team, said the findings explode the myth that the Y chromosome is primarily about the genes involved in male reproduction.

Now it is clear that the Y chromosome is not specific to males so to speak but also important for functions throughout the body, Professor Kaessmann said.

Men inherit both a Y and an X chromosome and women have two X chromosomes. However, scientists believe the Y chromosome is a withered remnant of the X chromosome from which it originally evolved. Hundreds of millions of years ago, genetic decay ravaged the Y chromosome, leaving it with just three per cent of its ancestral genes, compared with 98 per cent on the corresponding X chromosome of women.

This rapid loss of genetic function was widely seen as a portent of a premature demise for the Y chromosome, and of the male sex in general. The Oxford geneticist Professor Bryan Sykes, for instance, estimated in 2003 that men have about 125,000 years left before they become extinct.

However, the latest studies, published side by side in the journal Nature, demonstrate that although the Y chromosome has retained only 19 of the 600 genes it once shared with the X chromosome, it has lost only one of its genes in the past 25 million years, and those that have remained continue to serve vital functions throughout the male body.

This [study] tells us that not only is the Y chromosome here to stay, but we need to take it seriously; not just in the reproductive tract, Professor Page said.

Daniel Bellott, a research scientist at the Whitehead Institute, said: Evolution is telling us these genes are really important for survival. Theyve been selected and purified over time. We think that the Y chromosome is holding on to these last few genes to ensure male viability.

- The Independent

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