“Y” So Different?

Apr 19, 2018

By Rachel Cherney

While a baby is developing, it is by default, female. However, with the presence of the Y sex chromosome, the developing female will be overridden and instead develop a male reproductive system, thus becoming male. Males have an X and a Y sex chromosome, whereas females have two X chromosomes. Millions of years ago, males used to have two X chromosomes, just like females. What led to the Y chromosome’s formation and why do we care?

https://www.flickr.com/photos/nihgov/28189336441The sex chromosomes, X and Y, were originally like the other chromosomes, more commonly known as autosomes. They didn’t have the special functions they have today. However, several million years ago the proto-X and proto-Y chromosomes became distinguished from the autosomes when an error (also called a mutation) in a gene led to the formation of the SRY gene, which presently determines male sexual development. Over the course of millions of years,  animals continued to evolve and eventually, primates diverged from other mammals. At that time, an autosome gave the DAZ spermatogenesis gene to the Y chromosome, making it even more male specific due to the DAZ gene’s function in forming sperm. As the Y differentiated more and more from the X chromosome, there was less area for the X and Y to recombine. One important function of recombination is for getting rid of bad copies of genes. This loss of recombination led to the Y chromosome accumulating changes and deletions faster than the X, resulting in its fast deterioration rate and presently very small size.

https://www.flickr.com/photos/75358728@N05/7451093118Since much is still unknown about the Y chromosome, and due to its unique evolution, it is of considerable scientific interest and study. Researchers today are trying to understand what the different genes on the Y chromosome do, and if those genes contribute to more than just male sexual organ production or “maleness.” Recent studies have determined that some genes on the Y chromosome don’t only result in sex differences between males and females, but also are involved in maintaining men’s health. Understanding the differences between males and females in health and disease can lead to better, specialized treatments (to understand this concept, check out the definition of Personalized Medicine).

Not only does research of the Y chromosome give scientists and medical professionals a better idea of how the human body works, it can also provide an idea of how humans and other species have evolved over time, and what may happen to the Y chromosome in the future. There is a debate about whether the Y chromosome will disappear completely or not and is a divisive topic in the scientific community. Recent genetic studies have shown some genes on the Y chromosome increase in number, not only in humans, but in other mammals that also have the XY sex-determination system. This increase of certain genes helps to keep males fertile and reduces DNA loss on the Y chromosome. Even if the Y chromosome does disappear from the genome, it does not mean that there will be no more men. The genome is an incredible structure that will find a new, clever way to determine male and female.

 

Edited by Sam Stadmiller