And then there was Y: how the afterthought to the human Genome project broke the chromosomal mold.(Hot Papers)

The Y chromosome gets no respect. Regarded as a genetic junkyard with little to offer but sex, genomes have commonly rolled off the presses without a nod to Y. Then there's the matter of decay. Without a recombination partner, genetic insults whittle away the already diminutive Y, suggesting the chromosome's, and by extension man's, eventual extinction.

But this issue's Hot Papers refute the entrenched view of the Y chromosome. One showcases its sequence? and the other sizes up the male chromosome across humans and other primates. (2) The emerging picture turns out to be not so bleak for the fate of man. The studies reveal a crafty recombination method, ensuring Y's survival for generations. Recent work making comparisons with the completed chimpanzee genome has increased the clarity of the Y portrait, but also left a few new questions. (3)

AN IMPERFECT PAIR X and Y are believed to have arisen from a common autosomal pair that gradually diverged because of progressively impaired X-Y recombination. Y literally ended up with the short end of the genetic stick. Although some X-Y crossing over occurs during male meiosis, 95% of the Y chromosome is on its own, having no partner with which to recombine. Consequently, Y lost much of its size compared to the X chromosome. The genes on the Y chromosome were thought to rot over time without a backup copy or the ability to swap out through meiosis.

In 2003, geneticist David Page and colleagues at the Whitehead Institute for Biomedical Research in Cambridge, …