The remarkable endurance of the Y chromosome, ‘master of maleness’

Subject : Science and technology

Section: Biotechnology

Concept :

The Y chromosome, often referred to as the “master of maleness”, has long captivated scientists and historians alike.

Y chromosome

In humans, in addition to the 22 pairs of chromosomes in each, we have a pair of sex chromosomes called X and Y.
Sex as a specification is determined by these sex chromosomes. They carry sex-determining genes.
All biological males have X and Y chromosomes and all biological females have two X chromosomes.
The ‘sex-determining region Y’ on the Y chromosome determines the biological male sex.

‘Juvenile delinquent’

Estimated to have emerged around 200-300 million years ago in a common ancestor of all mammals, the Y chromosome has had a unique genetic journey, and embedded within its DNA lies a remarkable tale of evolution.
Scientists published the complete genetic sequence of the Y chromosome in 2003. This sequence provided an outline of 23 million bases of the 60 million or so bases that together make up the Y chromosome.
In total, the chromosome encoded for only 55 genes and accounted for around 2% of the genetic material inside a cell.
Many researchers jokingly refer to the Y chromosome as the “juvenile delinquent” among chromosomes pertaining to its abundance of repetitive sequences, poor functional utility (with a small number of genes), reluctance to socialise (i.e. recombine with other chromosomes), and a high proclivity to degenerate over the course of evolution.
Indeed, because it has little potential to recombine, the diminutive Y chromosome has been passed from father to son, carrying the legacy of generations.

Vital genes

In a landmark genetic study, published in March 2003 in the American Journal of Human Genetics, researchers reported that around 0.5% of all the men in the world have inherited a Y chromosome from the Mongol emperor Genghis Khan or one of his descendants.
Y chromosome possesses genes that are vital to biological functions, including those linked to ageing and lifespan regulation.
In the animal kingdom (including mammals), scientists have noticed substantial differences in lifespan between the sexes: the females tend to live longer than the males.
This phenomenon has been attributed largely to the absence of a second Y chromosome in males, exposing the deleterious mutations in the X chromosome.
It is also well known that men lose the Y chromosome with age and that this is associated with a higher frequency of cancers, Alzheimer’s disease, and a shorter lifespan.

Losing the Y

Studies have shown that LoY in humans occurs with age and is associated with several debilitating medical conditions – a finding that has been validated in mice with LoY, resulting in weak heart muscles (cardiomyopathy), stretched or thickened heart tissue (fibrosis), and heart failure.
researchers have also found that the pathological effects observed on account of LoY in mice’s hearts could be negated by transforming growth factor beta 1-neutralising antibodies, suggesting a potential treatment for this medical condition in future.
The human Y chromosome is about one-third as big as the X chromosome. So, many animal species, including humans, have a genuine fear of losing the Y chromosome in the distant future.