Biology Online is a Biology blog and dictionary site that provides up to date articles on the latest developments in biological science. The Biology Online Dictionary is a completely free and open dictionary with over 60,000 biology terms. It uses the wiki concept, so that anyone can make a contribution.
Tag: male chromosome

Men could go extinct? Y chromosome is slowly disappearing

Hold on to your seats, gentlemen — the male chromosome (Y chromosome) is slowly disappearing at a relatively fast rate and it might be gone completely in the future. This presumption is based on the genetic studies on the Y chromosome. It used to be genetically the same as the X chromosome. However, it has degenerated gradually, and now, it shriveled and became less relevant.

 

 

 

Y chromosome as male-determiner

Y Chromosome and DNA illustration. (Credit: Archaeogenetics, distributed by CC BY-SA 3.0 license)

 

Humans have two types of sex chromosomes: the X chromosome and the Y chromosome. Females have two X chromosomes whereas males have only one. Nonetheless, males have the Y chromosome that is passed on across generations from fathers to sons. In the XX/XY sex-determination system, the Y chromosome is the male-determining sex chromosome. Previously, the X chromosome was regarded as the sex-determiner. This conjecture, however, was eventually proven wrong when the SRY (sex-determining region Y) gene was identified on the male chromosome.1 This gene codes for the testis-determining factor, a protein that triggers testis development. Without this gene, testis fails to develop in males. There are few other genes present on the Y chromosome. However, compared with the X chromosome, the Y chromosome is relatively gene poor and the only highly notable gene on it is the SRY gene.

 

 

 

The disappearing Y chromosome debate

Going back in time, about 166 million years ago, the first mammals had a Y chromosome (called a proto-Y chromosome) that was genetically similar to and of the same size as the X chromosome.2 However, the male chromosome diminished into the short Y chromosome that it is now. The Y chromosome degenerates as it loses genes through time. Unlike the other chromosomes, the Y chromosome does not undergo genetic recombination. Based on the current speed of degeneration, the Y chromosome would likely have 4.6 million years left, which relatively speaking is not that long, considering the 3.5 billion years that life has existed on Earth.2 Some mammals, such as certain rodent species, have already lost their entire Y chromosome. 3 Some experts (referred to as the “leavers”) infer that this event would also happen to humans in the future. This notion was opposed by others (the “remainers”) who believe that the Y chromosome would not disappear completely because it has evolved corrective mechanisms that slow down and deter gene loss. Gene amplification (the acquisition of multiple gene copies) and the presence of palindromes (a sequence that reads the same, whether backward or forward, e.g. AGTGA) help mitigate gene loss.3

 

 

 

Men without Y chromosome in the future

Will men be extinct in the future?

 

If the Y chromosome ultimately disappears in the future, what will happen to men? Will there be men in the future? Experts believe that men will get by when that time comes. Men would still be around just as women have been perfectly fine without the Y chromosome. As for the SRY gene, it could move to a different chromosome. Nonetheless, the chromosome that would take this gene would be at risk of going through the same fate as that of the Y chromosome.3 The absence of SRY gene on the male chromosome is not new, however. In Swyer syndrome, the individual has a Y chromosome lacking the SRY gene and consequently fails to develop testis and other internal male organs. A person with this genetic condition is outwardly female but with a karyotype of a male (i.e. XY karyotype) .2

 

 

 

Further research on the degenerating male chromosome is essential to monitor the rate of gene loss on Y chromosome. One possible implication of the possible complete disappearance of Y chromosome is the impending necessity for more advanced reproductive modalities that can be applied artificially not just on humans but also on other mammals as reproduction by that time would ever hardly become natural.

 

 

 

— written by Maria Victoria Gonzaga

 

 

 

References:
1 “Y chromosome”. (n.d.). Biology-Online.org Dictionary. Retrieved from [https://biology-online.org/dictionary/Y_chromosome].
2 Griffin, D. & Ellis, P. (2018). The Y chromosome is disappearing – so what will happen to men?
Retrieved from https://theconversation.com/the-y-chromosome-is-disappearing-so-what-will-happen-to-men-90125
3 Griffin, D.K. Is the Y chromosome disappearing?—Both sides of the argument. Chromosome Res (2012) 20: 35. https://doi.org/10.1007/s10577-011-9252-1