A study from the University of Kent has been making the rounds on social media lately and sparked concern among netizens. The findings revealed that the Y chromosome is dwindling, which is primarily responsible for male sex determination. This has raised questions about the potential extinction of males altogether in the future.
Role
of chromosomes
Humans have 23 pairs of chromosomes in each cell. A chromosome is
a thread-like structure found in cells and is composed of the genetic material
of an organism. The 23rd chromosome pair is unique and determines the sex of
the baby. Females have a pair of X chromosomes, while males have one X and one
Y chromosome. The Y chromosome is the foundation of male biology and carries
SRY (sex-determining region Y gene) and is responsible for the formation of
testes in the embryo.
Deteriorating
Y chromosomes
Y chromosome is the base for male existence. It is passed from
male parent to male offspring. But it is not necessary for basic life
functions. X on the other hand has essential life genes, making it
indispensable. X chromosome has 900 protein-coding genes, while Y has only 100
protein-coding genes. Over time, the Y chromosome has a limited gene
repertoire, shrivelling and degenerating slowly.
However, this has not always been the case. 166 million years ago,
the Y chromosome was as gene-rich as the X chromosome. There’s an inherent
shortcoming, as the Y chromosome is the odd one out of the lot. All the
chromosomes exist in pairs, and each cell has two copies of each. But, the Y
chromosome is a single copy, unable to undergo genetic recombination. With two
copies of the chromosome, it is possible to get rid of damaging genetic
mutation by shuffling the genes after every generation. Y chromosome lacks the
benefits of genetic recombination and starts to shrink generation after
generation it keeps carrying the damaging genetic mutation, causing the
chromosome to degenerate.
Evolutionary
resilience
However, the Y chromosome shows resistance and adaptability. A
Danish study, published in PLoS Genetics, revealed that the Y chromosome
attempts to preserve itself and develops a particular DNA sequence,
palindromes, that essentially repairs the damaged genes. Here, undamaged genes
are utilised as a blueprint to fix the damaged ones. The study also illustrated
the likelihood of the Y chromosome’s structural rearrangement for gene
amplification, to maintain sperm health.
However, despite all attempts, the Y chromosome is continuing on
its path of decline. The Y chromosome has disappeared in Japanese spiny rats
and mole voles. In such a case, the SRY gene in the Y chromosome, responsible
for the male characteristics, would latch onto another chromosome. Y chromosome
would no longer determine sex, without the SRY gene. Although, it is doomed as
well, and the new sex-determining chromosome SRY gene has moved onto, would
experience the same degeneration as the Y chromosome.
Future
of reproduction
The dwindling Y chromosome raises concern for human reproduction
as the Y chromosome is essential for sperm production, and the continuation of
the species. With the aid of assisted technologies, many of the genes can be
bypassed. This implies that soon in the future, with the help of genetic
engineering same-sex female couples or infertile men might be able to have
children. But, even if it’s feasible, it’s unlikely to replace the natural
reproduction completely. As per the study, the Y chromosome’s disappearance is
set to happen 4.6 million years into the future. But it does indicate that the
future holds a new system of sex determination, reproduction, or if anything,
an entirely new species.
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