Recently, a University report has been circulating on social media, raising concerns among online users. The results showed that male sex determination is predominantly caused by a shrinking Y chromosome. This has sparked concerns about the possibility that men would eventually go extinct.
What is the function of chromosomes?
Each human cell contains 23 pairs of chromosomes. A chromosome is a thread-like structure made up of an organism’s genetic material that is located in cells. The sex of the child is determined by the unique 23rd pair of chromosomes. Males have one X and one Y chromosome, while females have two X chromosomes. The Y chromosome, which contains the SRY (sex-determining region Y) gene and is essential for the development of the testes in the embryo, is the cornerstone of male biology.
There are several variances and some similarities between X and Y chromosomes for sex. Generally speaking, a girl has two XX chromosomes while a male has one X and one Y chromosome. Maleness, sex determination, and differentiation are mostly linked to genes found on the Y chromosome and Y-linked features.
A Decline in Y chromosomes
The male chromosome serves as the foundation for life. Male parents pass it on to their male children. However, it is not required for essential living activities. On the other hand, X is necessary since it possesses vital life genes. There are 900 protein-coding genes on the X chromosome and just 100 on the Y. The Y chromosome gradually withers and degenerates due to its restricted gene repertoire.
This hasn’t always been the case, though. The Y chromosome has the same abundance of genes as the X chromosome 166 million years ago. Because the Y chromosome is the unique one among the others, there is an intrinsic defect.
Each cell contains two copies of every pair of chromosomes. However, the Y chromosome can only occur in one copy and cannot be genetically rearranged. By randomly rearranging the genes after each generation, harmful genetic mutations can be eliminated in organisms with two copies of each chromosome.
The Y chromosome degenerates because it lacks the advantages of genetic recombination and begins to diminish with each successive generation. This is because it continues to carry the harmful genetic mutation.
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Structure of Chromosomes
It is true that the Y chromosome has a “Y” form. However, that is not the shape from which the term “Y chromosome” originated. Its companion is referred to as the “Y chromosome” since the other chromosome in this group is the X chromosome.
It has two chromosomal arms, a centromere in the middle, and telomeres at both ends, just like other chromosomes. The Y chromosome is an acrocentric, smaller chromosome structurally. Its arms are arranged as a short “p” and a long “q.” The majority of the genes and DNA sequences required for maleness, such as the TDF (Testis Determining Factor) and SRY, are found on the ‘p’ arm.
The Y chromosome has 100–200 identified genes and is roughly 59 million base pairs in size. We only know the functions of 40–75 genes, though. In most other mammals, the Y chromosome is nearly identical.
For example, there is only a 30% difference in sequence, not in size, between the Y chromosome of our nearest relative the chimpanzee.
Evolutionary robustness
On the other hand, the Y chromosome exhibits flexibility and resistance. According to a Danish study that was published in PLoS Genetics, the Y chromosome creates palindromes—a specific DNA sequence—in an effort to protect itself and effectively fixes damaged genes. In this case, the broken genes are fixed using the undamaged genes as a blueprint. The possibility of structural rearrangement of the Y chromosome for gene amplification in order to preserve sperm health was also demonstrated by the study.
Nevertheless, the Y chromosome is still declining in spite of all efforts. In mole voles and Japanese spiny rats, the Y chromosome has vanished. In this scenario, the Y chromosome’s SRY gene, which codes for masculine traits, would attach itself to a different chromosome. Without the SRY gene, the Y chromosome would no longer determine sex. It would, however, undergo the same degradation as the Y chromosome as it is also doomed and the new sex-determining gene, SRY, has moved on.
Reproduction’s future
Since the Y chromosome is necessary for sperm production and the survival of the species, its decline raises questions about human reproduction. It is possible to avoid many of the genes with the use of aided technology.
This suggests that same-sex female couples or infertile men may soon be able to conceive thanks to genetic engineering. Even if it were possible, natural reproduction would probably still be the primary method.
The study estimates that it will take 4.6 million years for the Y chromosome to vanish. However, it does suggest that a new reproductive and sex determination system—or perhaps a completely different species—may exist in the future.
