The Y chromosome, the “keeper of all things male,” has over time shrunk smaller and smaller, leaving many to wonder if the evolution of the male chromosome will lead to its eventual demise. Of course, the change in the size of the chromosome has occurred over millions of years, so any real sign of change would not be expected for quite some time. But nonetheless, it has prompted many researchers to imagine a future when male attributes would have to find another way to hitch a ride into future generations: perhaps even leading to a new dawn of immaculate conception.
A group of scientists led by David C. Page and Jennifer F. Hughes, at the Whitehead Institute of Cambridge, Massachusetts, have worked hard to piece together the long history of the Y chromosome in order to get a better idea of where it would be going in the future. What they found was that despite a history of dramatic change, the Y chromosome has all-in-all hit a lull that has lasted some 25 million years. According to Page and his colleagues, the Y chromosome has gone through a series of stages that began approximately 320 million years ago, when the chromosome first appeared and culminated in the decreased size of the chromosome through the millennia.
In its earliest stages, both the Y and the X chromosome were the same size and held the same number of genes. Now, the sides are severely skewed with the Y chromosome containing no more (and possibly less) than 30 genes to the X’s estimated 800. This has happened because of the Y’s “self-sacrificing” of its own genes in order to lend a hand and safeguard the feminine X. In doing so, a sort of no-swap area was determined on the Y chromosome in order to protect the Y chromosome from complete eradication. And over the millions of year since its first appearance, this no-swap area has gradually grown to encompass practically all but the very tips of the chromosome.
It is because of this self-effacement that the Y chromosome now contains much fewer genes than it once had. However, that is not to say that the Y chromosome is not important. In fact, it is because the chromosome contains such important attributes, namely, the male genes and the gene that determines sex that the Y chromosome will never completely disappear— at least not any time soon. “We can confidently say that the decay of the Y chromosome has come to a halt, and that would portend very well for its future,” explains Hughes. “If you draw a straight line, the Y chromosome’s demise would come four or five million years from now,” adds Darren Griffin, a professor of genetics at the University of Kent in Canterbury.
Researchers gained this insight by breaking down the genetic code of the rhesus monkey, an animal that shares a common ancestor with humans from the same time that the Y chromosome last gave up many of its genes. Because of this new information, believers of the “rotting Y” theory can rest assured that the Y chromosome will be here for a while. “It’s my sincere hope that this article might put the notion of the disappearing Y chromosome to rest,” adds Page confidently.
And for now anyway, it seems that it has.
Photo Credit: nist.gov/mml/biochemical/images/y_chromosome.jpg