Males aren't disappearing, scientists conclude

By Sheilah Downey

The male sex chromosome that only males carry is deteriorating and could disappear entirely within a few million years, scientists at Penn State say.

But it's not the end of the male.

The Y chromosome, carried only by males, has evolved at a much higher pace than the X chromosome, which is carried by both men and women. This rapid evolution, say researchers, has led to a dramatic loss of genes on the Y chromosome that could lead to mutations down the evolutionary path.

"Even though some of the genes appear to be important, we still think there is a chance that the Y chromosome eventually could disappear," said research team leader Kateryna Makova in a Penn State press release. "If this happens, it won't be the end of males. Instead, a new pair of non-sex chromosomes likely will start on the path to becoming sex chromosomes."

The Y chromosome contains less than 200 genes, said Makova, while the X chromosome has around 1,100 genes. Some of the genes are essential to life, she said, while others were lost over time.

"We know that a few of the genes on the Y chromosome are important, such as the ones involved in the formation of sperm," she said, "but we also know that most of the genes were not important for survival because they were lost, which led to the very different numbers of genes we observe between the once-identical X and Y."

The research team plans to create a computer model that tracks the degeneration of the Y chromosome to determine how long it will take for it to disappear. They also hope to identify the processes that are most important for degeneration of the Y chromosome.

Makova, associate professor of biology, and National Science Foundation Fellow Melissa Wilson published their findings in the July 17 issue of the journal PLoS Genetics.