The human Y chromosome is in the process of degeneration and could disappear in several million years, leading to the extinction of people, if we do not develop a new sexual gene, warns the researchers.
Foto chromosome: shuterstock
The good news is that two species of rodents have already lost their Y chromosome, but have survived.
In humans, as in other mammals, females have two X chromosomes, and males have a single X and a Y chromosome. It contains about 900 genes that fulfill various roles that are not related to sex. But Y contains few genes (about 55) and a large amount of non -unmixing DNA – simple repetitive DNA, which does not seem to do anything, according to Earth.
But the Y chromosome also contains an extremely important gene, which starts the male development in the embryo. About 12 weeks after conception, this main gene gives the start of other genes that regulate the development of the testicle.
The embryonic testicle produces male hormones (testosterone and derivatives), which makes the baby develop as a boy. This main gender gene was identified as Sry (sexual region on Y) in 1990.
It works by triggering a genetic path that begins with a gene called SOX9, which is the key to male determination in all vertebrates, although not on sexual chromosomes. Most mammals have X chromosomes and Y as ours; an x with many genes and a y with Sry and a few more. This system comes with problems, due to the unequal dose of gene x in men and women.
Comparative studies in mammals show that once our nation has separated from the pride 166 million years ago, Y began to lose about five genes every million years. Going through this line, the register reaches zero in 11 million years – a geological heartbeat.
Most biologists once considered that this result is an illusion. After all, many species have never lost their sex chromosomes. But the idea has gained magnitude when the researchers found that the Japanese Tepos Rat and some species of prosperous mumps today without any Y. Somehow, they restored the traditional circuit of testicles.
Rodents changed the rules
In 2022, scientists discovered a piece of duplicate DNA near a gene called SOX9 in the Tepos Rat. Usually another gene (SRY) activates SOX9 to develop male features.
But at this rat, the new copy of DNA does its own job – even without a Y chromosome – so that a female genetic animal (XX) can continue to develop as a male.
This discovery suggests that if Y human disappears on a distant day, the natural selection could promote an alternative trigger.
Different populations could even settle on different triggers, eventually divided into separate species that cannot be crossed. The idea sounds science fiction, but the reality of rodents shows that it is genetically feasible.
Y chromosomes and men’s health
Long before any species review, countless men already lose the cell chromosome. Starting with the age of 50, the stem cells in the bone marrow sometimes separated it during the division.
The resulting white cell lines, which are missing y, multiply quietly. Up to the age of 80, over 40 % of men carry considerable pockets in the blood of this “Mosaic of loss Y”.
Following 1,153 Swedish men between the ages of 70 and 80, the researchers found that those who had this loss died 5.5 years earlier, suffered several solid tumors and heart disease and faced an increase in Alzheimer’s cases.
Kenneth Walsh of Virginia’s University then raised mouse blood cells without the Y chromosome and transplanted them. The recipients developed fibrosis, heart failure and early death, demonstrating that the loss is guilty, not a spectator.
Direct bond to the immune system
A gene from the Y chromosome called UTY helps control the immune system. Without it, some immune cells no longer work properly – one type produces more scar tissue, and the other becomes weaker, which helps to increase and spread cancer.
The image is complicated: a chromosome underlying the male development also softens inflammation and limits tumors, but its selective absence can cause some drugs to shine.
Medicine and evolution rarely share the same conclusion. The natural selection values reproductive success throughout the life, while doctors are concerned about here.
Counteracting the loss of chromosome y
Cigarette smoke, air pollution and certain industrial chemicals cause additional DNA damage and accelerate the loss of Y chromosome. Retning from tobacco, breathing cleaner and limiting exposure to mutagenic agents are therefore simple defense measures – only will.
General habits that slow down genomic wear – regular physical exercises, Mediterranean style and deep sleep – can also keep Y chromosome in more cells for longer.
Antiphibrotic drugs approved for lung disease are under testing to alleviate heart lesions. Oncologists already use chromosome status in bladder tumors to direct control points therapy.
As the sequence of a single cell becomes cheaper, the physical examination could soon include a “loss score”, in addition to cholesterol.
What will we do from now on?
The Japanese thorny rats prove that mammals can reinvent the rules after disappearance “Little chromosome”. This perspective holds evolutionary biologists.
However, the triumph of rodents offers a little consolation to a 60 -year -old man whose marrow has already lost one third of his white globe army.
Saving at the species level and the danger at the individual level can coexist. This dichotomy – long -term adaptability versus immediate personal costs – will probably guide both medical practice and evolutionary debate in the coming years.
The Y chromosome is weird, but crucial. It shapes male development, stabilizes immunity and could also make its own disappearance.
