The Y chromosome is slowly degenerating

So far, we have always attributed the Y chromosome to the symbol of masculinity. But it turns out this type of chromosome is not as strong and durable as we imagined.

Although this chromosome carries on it the miraculous sex switch SRY , which determines the sex of the embryo, it does not carry many other genes and is the only chromosome that is not necessary for life. Indeed, women do not need this chromosome and still live well.

The Y chromosome is slowly degenerating, the X chromosome in women is still completely normal.

Not only that, the Y chromosome is slowly degenerating, whereas the X chromosome in women is still completely normal. According to calculations, if this rate of degradation continues, only in 4.6 million years, this type of chromosome will completely disappear. It sounds like a long time, but it is only a very short time if we calculated from the beginning of life on Earth 3.5 billion years ago.

After hundreds of millions of years, the Y chromosome was not intact compared to before. If we go back to 166 million years ago to learn about the chromosomes of the first mammals, we will get a completely different story. The first "prototypes" of the Y chromosome are similar in size to the X chromosome and contain many other genes. However, on the Y chromosome there is a structural flaw. Unlike other chromosomes, Y appears only as a single copy, transmitted from father to son.

This means that the genes on this chromosome cannot undergo genetic recombination , which means that it cannot participate in the genetic permutation that occurs in each generation, in that it cannot Eliminate gene mutations. Because of the lack of benefits of this process, the Y chromosome gradually degenerates, and it may completely disappear from the genome someday.

However, some recent studies have shown that the Y chromosome is developing several mechanisms that promise to help "brake" this process, helping to reduce the rate of gene degradation almost to nil.

For example, in a recent study by the Danes and published on PloS Genetics , the sequence of Y chromosomes was resolved in 62 men. They discovered the trend of an ongoing refactoring, which allowed the "gene amplification" process to work, which would capture many different copies of the gene to help promote function. healthy sperm and reduce the amount of gene loss.

Genetic techniques will soon replace the function of the Y chromosome.

The study also showed that the Y chromosome also developed many other new types of structures called palindromes , which are DNA sequences that, whether read or reverse, produce identical sequences. This new type of structure will help protect it from possible future recessions. The team recorded a series of " gene conversion events " that occur in the palindromes sequence on the Y chromosome. Simply put, these events are a copy and paste process, it gives permission to repair damaged genes through templates is undamaged backups.

If we look at other species (Y chromosomes that exist in mammals and some other animals), there will be an increasing amount of evidence emphasizing that gene amplification is a Common rules in species that carry this chromosome. These amplified genes play a major role in sperm production and regulate the sex ratio at birth. In an article published recently in Molecular Biology and Evolution , the researchers also provided more evidence that the increase in the number of genes copied in mice is the result of self-selection. Of course.

However, when answering the question: whether the Y chromosome disappears, the scientific community is divided into two opposing factions. One side argues that the Y chromosome's self-defense mechanism helps to save this type of chromosome. But the opposite side believes that this mechanism is just a bit of an effort to help this chromosome cling to the edge, sooner or later, it will fall down only. The debate between these two opposing views will continue.

A prominent person in the view that the Y chromosome will soon slip, Ms. Jenny Graves from La Trobe University in Australia asserts that if we look under the long-term perspective, there will be no future It is good for this type of chromosome, although sometimes this mechanism will help it fend off for a longer period of time than previously anticipated. In a study published in 2016, she showed that in Japanese thorny rats and mole rats, the Y chromosome completely disappeared. She also argues that new gene loss and creation processes on the Y chromosome will inevitably lead to reproductive problems. The result of these problems may be the formation of completely new animals.

Will men suffer "extinction"?

There are many arguments that even if the Y chromosome completely disappears in humans, it does not mean that men will disappear forever. Even in animals that have lost the Y chromosome, the male and female individuals are still essential for the reproductive process.

In these species, the sex switch SRY has been transferred to another chromosome, meaning that males of this species can still be created without the presence of the Y chromosome. This new sex-regulated chromosome will also have problems similar to the previous Y chromosome, which will start to degenerate again.

The good news for humans, however, is that even though the Y chromosome is essential in human reproduction, many types of genes that it contains are not necessary if we use assistive technologies. reproductive aid. This means that genetic engineering will soon be able to replace the function of the Y chromosome, and allow lesbian or male infertile couples to conceive. But the appearance of this type of conception does not mean that humans should abandon the usual method of reproduction.

Although this is a hotly sold topic in the field of genetic research, we don't have to be too worried. Currently, we have not even found a general conclusion to the question of whether the Y chromosome disappears. And even if it no longer exists, we still need both genders to continue the reproduction as usual.

And especially the "farm" scenario, where some male individuals are fortunate enough to be chosen as the father of the majority of individuals born will never happen. Even if there are any events that happen, this problem is not something we need to worry about in 4.6 million years.

1. Shocking detection of Y chromosome
2. Chromosome story X: Evolution of a sex chromosome