A recent study claims that the Y chromosome, which contains the SRY gene responsible for the development of a man, is reducing in size. Does this imply a female-centric world soon? Are the number of men declining? Here’s all you need to know.
What Is The Y Chromosome?
Humans have two sex chromosomes, namely X and Y, which determine the gender of the foetus. Men have both chromosomes in their cells while women have two X chromosomes in each of their cells.
Humans have 23 pairs of chromosomes, one pair of which determines the gender of the child. While females have two X chromosomes (XX), men have one X and one Y chromosome (XY).
What happens during fertilisation is that the sperm cell, containing either an X or a Y chromosome fuses with the egg cell, which always contains an X chromosome. If a sperm having an X chromosome combines with the egg, the embryo develops into a female whereas if a sperm containing a Y chromosome fuses with the egg, the embryo develops into a male.
3 months after conception, the SRY gene, also known as the master gene in the Y chromosome, triggers a genetic mechanism, by activating another gene called SOX9. This process helps in the development of the male reproductive organs.
What Does The Study Say?
A recent study that has gained quite a lot of attention claims that the Y chromosome is declining. Professor Jenny Graves explained this idea through a platypus.
“In platypus, the XY pair is just an ordinary chromosome with two equal members,” she said. “This suggests the mammal X and Y were an ordinary pair of chromosomes not that long ago. In turn, this must mean the Y chromosome has lost 900 to 55 active genes over the 166 million years that humans and platypus have been evolving separately. That’s a loss of about five genes per million years. At this rate, the last 55 genes will be gone in 11 million years,” she said.
Jennifer A. Marshall Grave, a Professor of Genetics and Vice Chancellor’s Fellow, also says that the Y chromosome is “running out of time.” if this is how it goes, it might completely vanish in 11 million years.
A report published in ‘The Week’, an Indian news magazine, explains the reason behind this. It stated that most of the Y chromosome consists of ‘junk DNA’. “With such an unstable composition, the Y chromosome is at risk of completely disappearing over the course of multiple generations,” said the study.
The report further analysed that since men have only a single copy of the chromosome, it does not get enough chance to undergo genetic recombination, that is, “shuffling of genes that occurs in each generation which helps to eliminate damaging gene mutations”. Y chromosomal genes degenerate over time in the absence of reshuffling.
Read More: Man Turns 10 Years Younger In Science Experiment; Here’s How
Will The Number Of Men Decline Soon?
To this question, Professor Graves explained, “When humans run out of Y chromosome, they might become extinct (if we haven’t already gone extinct ourselves long since), or they might evolve a new sex gene that defines new sex chromosomes.“
She added that while certain species of lizards and snakes are female-only, this cannot be the case for human beings because we have about 30 “imprinted” important genes that come only from the father’s sperm.
This question has also divided scientists into two groups, namely the “leavers” and the “remainers”. While the former believes that the Y chromosome will cease to exist at the rate at which it is declining, the latter argues that defence mechanisms will do their work and we will continue to have this type of chromosome.
Another study published in ‘Proceedings of the National Academy of Science’ shows how spiny rats have evolved a new gene for the determination of the male gender.
The study exhibits how the Y chromosomes and SRY genes of the spiny rats of Japan and the mole voles of Eastern Europe, have been lost down the line, yet the species have survived. The findings imply that even when the Y chromosome disappeared, a new mechanism for the determination of gender could evolve.
Similarly, Caenorhabditis elegans, a common lab species of nematode worms, has two forms – a male and a hermaphrodite, which are male as larvae and become females later in their life span. When at the stage of larva, they make and store sperm and when they evolve into female organisms, they gain the ability to make eggs, which they fertilise with the stored sperm.
“The Y chromosome’s loss has not been fatal for the spiny rat; instead, it has adapted by finding an alternative way to determine sex,” said the study, led by Asato Kuroiwa at Hokkaido University.
Scientists believe that “We could see the rise of several distinct human species, each with its own unique sex-determining mechanism.” So, if someone visited our planet in 11 million years, they might find diverse human species, differing in their sex-determination systems.
However, even though the occurrence of new species is quite intriguing, it creates a zillion questions about their survival in the world.
Image Credits: Google Images
Feature image designed by Saudamini Seth
Sources: The Economic Times, The Financial Express, Firstpost
This post is tagged under: scientists, men, women, male, female, sex, gender, chromosomes, study, report, species, human beings, Earth, Hokkaido University, Asato Kuroiwa, rats, Europe, Japan, eastern, Proceedings of the National Academy of Science, lizards, genetic, DNA, foetus, gene
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