Apparently it is likely that the Y chromosome, fundamental for determining the development of the male biological sex in our species, remains running out of timeand its extinction is expected within 10 million years. This is due to the fact that this chromosome continues to shrink and that the active and truly useful areas are very few. To be clear, in humans the male sex is established by the presence of an X chromosome and a Y chromosome, while the female sex is established by the presence of two recombination (exchange of genetic material) with the X chromosome to which it is paired and consequently collects useless gene sequences which are subsequently degraded. If initially (166 million years ago) the Y chromosome had almost 1700 genes, today it contains just 45. Furthermore, it is located in a inhospitable environmentthe testes, with the wide possibility of suffering mutation problems or not being transmitted if the person decides not to have children. This does not mean the extinction of the male gender, since there have already been cases of other species in which the male specimens have lost the Y chromosome: they have simply implemented another genetic strategy to have the same result.
What is the Y chromosome for and is it true that we are losing it?
The sex chromosomes are the only pair of chromosomes that are different from each other: we all have at least one X chromosome inherited from our mother in the fertilized egg, and another chromosome (which can be X or Y) carried by the sperm that fertilizes. The association of XX or XY determines the sex of the unborn child: an XX chromosomal combination is specific to female development and XY to male development. While the X chromosome contains many genes and therefore a lot of information, the Y contains many repeated sequencesAnd few useful genes: those that activate training for testicular development and a few others.
The molecular science expert Jenny Gravesprofessor and geneticist at theLa Trobe Instituteis one of several scientists who support the probable and slow disappearance of the Y chromosome between the 4.6 million years hey 10 million years. This hypothesis is supported by various scientific evidence, but no certainties can yet be maintained in this regard. Currently the Y chromosome has approx 45 geniuses and it started from around 1700 genes originally. If the trend of progressive shrinkage continued to be this, the loss rate could lead to the extinction of this chromosome.
Why is the Y chromosome degrading?
All other chromosomes, other than X and Y, they recombine between them, that is to say that they exchange genetic information (pieces of chromosome) during meiosis (cell division), to have more genetic variation and eliminate any deleterious mutations.
The Y chromosome, however, being different in size, shape and function from its X counterpart, cannot recombine with any other chromosome, therefore it tends to accumulate deleterious mutations. He can only make one specific internal recombination to itself, which compensates a little for the lack of recombination between two different Y chromosomes. This is one of the reasons why the Y chromosome it gets shorter and shorter: accumulates deleterious mutations, i.e. useless parts that tend to be eliminated over time.
This degradation, for now therefore, only concerns areas with accumulations of deleterious mutations. It is not clear, however, whether the genes of the Y chromosome can be partly maintained permanently – because they are somehow “useful” – or whether a complete collapse may be imminent. For example, the SRY regionin particular, could be maintained and remain the only one in existence, since it contains the information for the development of masculine characteristics and therefore determines sex. We only know that we have examples where male-specific genes, including the SRY gene, have been lost in some mammalian species.
There are other reasons why the Y chromosome degrades, and is therefore likely to disappear, for example the fact that this chromosome is passed down from generation to generation only in the testes. In fact, they happen inside the testicles many cell divisionssince there is a need to continuously produce sperm. These numerous meioses increase the probability of having DNA damage that cannot be corrected: consequently they reduce the chances of the Y chromosome to survive and increases the probability of transmit a deteriorated variant of Y to the children.
Furthermore, if major recombination cannot occur and there are particularly healthy and undamaged Y chromosomes, these could be lost forever if the bearer decides not to have children and that chromosome is consequently not inherited.
If the Y chromosome disappears, will the males of the human species also disappear?
It must be said that, despite the scientific evidence of the shrinkage of the Y chromosome, we cannot exclude the possibility that it does not disappear and is maintained, given that we are still talking about a projection from here to at least 4.6 million years.
But, even if the Y chromosome were to disappear, It doesn’t mean that males will disappear. There are mammalian examples (the most obvious being in the Japanese rat of the genus Tokudaia) in which the Y chromosome has dissolved, but various mechanisms for determining male sex have been established. Much more likely, therefore, if the Y chromosome were to become extinct, they will evolve new sex-determining genesand the differentiation of the sex chromosomes will begin again.
Furthermore, human beings are not a species parthenogenetic (that process in which the egg cell does not need the sperm to be fertilized), so it is difficult for the male itself to disappear. In general, males and females of the human species are more or less the same in number. Given this trend, it is difficult for everything to change, leading to the complete disappearance of males and therefore to an imbalance of the sexes. In fact, males are still necessary for human reproduction, excluding the cloning approach.
