New studies indicate that the Y chromosome in humans is in decline and may disappear within a few million years, which could lead to our extinction… but a new study may offer a different opinion.
It is known that in humans, as in mammals, females have two X chromosomes, and males one X chromosome and a tiny little chromosome called Y. The X contains about 900 genes that perform all kinds of non-sex functions. But Y contains few genes (about 55) and a lot of noncoding DNA — simple repetitive DNA that doesn’t seem to do anything.
The importance of the Y chromosome lies in the fact that it contains a very important gene, called SRY, because it contributes to determining the sex of the fetus, and begins to interact 12 weeks after fertilization.
However, previous studies showed that the Y chromosome was losing about 5 genes every million years, and that is why their number decreased from 900 genes 160 million years ago to 55 now.
If this trend continues, this chromosome may disappear completely after 11 million years, according to several theories.
The good news, however, is that two branches of the rodents did indeed lose their Y chromosome, but were able to persist. A new paper published in the Proceedings of the National Academy of Sciences reveals how the spiny rat developed a “new gene” for males.
The study indicated that some species of mole rats in Eastern Europe and spiny rats in Japan had completely disappeared the Y and SRY chromosomes, and remained with the X chromosome in a single or double dose in both sexes.
Although it is not yet clear how mole rats determine sex without the SRY gene, a team from Japan’s Hokkaido University reports that most of the genes on the Y of spiny mice have moved to other chromosomes. However, the team found no trace of the SRY gene, nor the gene it replaces.
Instead, the team found genetic sequences that were only found in male mice and not in females. These sequences can trigger the major sex gene SOX9 to function without the presence of SRY.
This new study supports theories that humans can survive if they develop a new gene that determines sex.