The Y chromosome has an expiration date. Although it is the only one capable of defining the male sex in humans and other mammals, it is smaller, weaker and less genetically complex than the X chromosome. However, its extinction may not be certain: a gene capable of killing it is also your life insurance.
The Y chromosome is only present in the males of most mammals and some other animals. It has an important role in determining the sex of the embryo. Of the 23 pairs of chromosomes that make up the human genome, the last one defines sex. If there are two XX chromosomes, the human being will be a woman, and if it is an XY pair, it will be a man.
Science maintains that the Y chromosome will be extinct in 10 million years due to genetic degradation that has occurred throughout evolution. Because it is present only in men, it cannot pair to recombine and repair itself genetically.
However, two researchers from Australia and Spain go against the grain with their persistent Y hypothesis, according to which the Y chromosome will not die out. For Paul D. Waters, an expert in Biotechnology and Biomolecular Science at the University of New South Wales, and Aurora Ruiz-Herrera, from the Institute of Biomedicine and Biotechnology at the Autonomous University of Barcelona, the key lies in the cell division that allows the creation of gametes, that is, the process of meiosis.
In an article published in the scientific journal Trends in Genetics, both argue that a gene on the Y chromosome, which is of great importance during meiosis and even capable of killing the chromosome itself, is also responsible for preventing its extinction. How?
The hangman gene, the friend gene
The meiosis is a successive division of diploid cells (cells with two sets of chromosomes) to form four haploid cells (with one set of chromosomes), i.e., is the process that allows the formation of male and female gametes (ovum and sperm).
During male meiosis, the Meiotic sex chromosome inactivation (MSCI) takes place. That is, the X and Y chromosomes are “silenced” for meiosis to be successful.
MSCI could be triggered by differences in the genetic structure of the X and Y chromosomes. During meiosis, a part of the chromosomes cannot link to each other because of their divergences, which causes silencing thanks to a gene called Zfy.
Also, for meiosis to be viable, the Zfy gene itself must remain silenced. If the gene were activated during this stage, it would cause sperm death. For this reason, the Zfy gene is called an executor, since it is responsible for carrying out apoptosis (programmed cell death).
MSCI is of vital importance, as is the ability of the executor gene to “kill” defective sperm after failed meiosis. It has been proven that in mice that do not have a correct silencing during meiosis a mutation has occurred that renders them infertile.
For scientists, according to the persistent Y hypothesis, “the future of the Y chromosome is secure because it carries executor genes that are critical for male meiosis to progress successfully, and, unlike other Y genes, these executors are self-regulating”.
“Essentially, it acts as his own judge, jury and executioner, and in doing so, it protects the Y so that it does not get lost,” they say.