Featured image source: Photo by National Cancer Institute on Unsplash
The determining factor for the gender of an individual is present at the genetic level. A set of expressed genes present in a chromosome, the condensed and complex form of DNA, is what decides certain observable traits. In humans, we have two sex-determining chromosomes, one being the X and the other being Y. Two of X make up the feminine gender, whereas one of X and one of Y make up the masculine gender. At the beginning of human evolution, both X and Y chromosomes were almost of the same size, but now the Y chromosome has been reported to be shrinking in size. In fact, according to a prediction by Graves, the estimated time in which the Y chromosome will be completely gone is around 4.6 million years from now. The original ancestral genes, which were functional, have already been lost during their lifespan.
The function of the Y chromosome has always been a cause for debate in the scientific community. The Y chromosome seems to contain the master switch gene SRY, which determines whether the human life form will be male or female. Subsequently, there is also a change in the hormones that play a crucial role after the sex determination step. There are few similarities between X and Y; about 5% of the total chromosomal region of Y contains somewhat of a dozen genes which are also found in the X chromosome. But the majority or most of it is not anywhere close to being the same. It forms what is called the male-specific Y (MSY) region. Specificity is what defines the chromosomal region. It also explains the lack of a homologous pair has impaired its ability to evolve into fitter genes. It does undergo recombination, but that’s intrachromosomal, resulting in genes getting recirculated within themselves. Consequently, there is gradual loss of genes which further amounts to degeneration and degradation. As Darwin had theorized the idea of ‘Survival of the fittest’, chromosomal fitness is crucial for its subsistence. It seems like the days of Y are numbered.
The profound implication of dwindling of the Y chromosome has become a cause for concern among men. Due to the accumulation of deleterious changes (mutations), there may be high chances of cancer and other genetic disorders. Not just that, the Y chromosome has been seen to be missing in certain cells of the blood owing to the explanation that some genetic variants might be detrimental. Although the demise of the Y chromosome seems imminent, there is counter-evidence stating the presence of multiple copies of genes (also known as palindromic sequences) which might delay the buildup of harmful mutations. Not just that, there is increasing evidence of strong positive selection for the Y chromosome. Now, the core idea of balance between the constructive and destructive forces acting on it is questionable. It seems like the latter is dominating which could be a cause of concern. Therefore, the question of the fate of the Y chromosome still looms, the answer to which only time will tell.
