By NICHOLAS WADE APRIL 23, 2014
There is new reason to respect the diminutive male Y chromosome.
Besides its long-known role of reversing the default state of being female, the Y chromosome includes genes required for the general operation of the genome, according to two new surveys of its evolutionary history. These genes may represent a fundamental difference in how the cells in men’s and women’s bodies read off the information in their genomes.
When researchers were first able to analyze the genetic content of the Y chromosome, they found it had shed hundreds of genes over time, explaining why it was so much shorter than its partner, the X chromosome. All cells in a man’s body have an X and a Y chromosome; women’s have two X chromosomes.
The finding created considerable consternation. The Y had so few genes left that it seemed the loss of a few more could tip it into extinction.
But an analysis in 2012 showed that the rhesus monkey’s Y chromosome had essentially the same number of genes as the human Y. ...
Dr. Kaessmann calculates that the Y chromosome originated 181 million years ago, after the duck-billed platypus split off from other mammals but before the marsupials did so.
... “Throughout human bodies, the cells of males and females are biochemically different,” Dr. Page said. The genome may be controlled slightly differently because of this variation in the 12 regulatory genes, which he thinks could contribute to the differing incidence of many diseases in men and women.
Differences between male and female tissues are often attributed to the powerful influence of sex hormones. But now that the 12 regulatory genes are known to be active throughout the body, there is clearly an intrinsic difference in male and female cells even before the sex hormones are brought into play.
“We are only beginning to understand the full extent of the differences in molecular biology of males and females,” Andrew Clark, a geneticist at Cornell University, wrote in a commentary in Nature on the two reports.