A male-determining gene on chromosome Y determines the sex of mammal and human babies. The human however, Degeneration of the Y chromosomeWithout a new sex genetic, we may all disappear within a few million years.
Good news: Two branches of rodents already have their Y chromosomes lost and have survived.
A new paper Proceedings of National Academy of ScienceThis shows how the male-determining gene in the spiny rat evolved.
How the Y-chromosome affects human sex
As in all mammals, humans have two Xchromosomes. Females have one Xchromosome and a tiny Ychromosome. The names do not reflect their shape, the X stands for ‘unknown.
There are about 900 genes in the X that perform jobs not related to sex. However, the Y also contains Only a few genes (around 55). A lot of non-coding DNA exists – simple repetitive DNA that doesn’t seem to do anything.
The Y-chromosome, however, packs a punch. It contains an essential gene that initiates male development in the embryo.
This master gene is activated approximately 12 weeks after conception to regulate the development and growth of the testis. The embryonic testis is responsible for making male hormones (testosterone or its derivatives), which ensures that the baby grows up as a man.
This master sex gene was named SRY (sex regions on the Y). In 1990. It triggers a genetic pathway that begins with SOX9, which is the key to male determination in all vertebrates. However, it doesn’t lie on sexchromosomes.
The disappearing Y
The X and the Y chromosomes are very similar in mammals. The unbalanced X genes between males and women can cause problems.
How did this strange system develop? Surprisingly, the surprising result is that Australia’s platypusDifferent sex chromosomes exist, and they are more similar to those of birds.
The XY-Y pair in platypus is an ordinary chromosome with two equal members. This means that the mammal X was not a normal pair of chromosomes when it first appeared.
In turn, this must mean the Y chromosome has lost 900–55 active genes over the 166 million years that humans and platypus have been evolving separately. This represents a loss of approximately five genes per one million years. The last 55 genes are likely to be lost at this rate. 11 million years.
Our claim about the imminent death of the human species Y Created a furore, to this day there are claims and counterclaims about the expected lifetime of our Y chromosome – estimates between infinity and It took a few thousand of years.
Rodents that lack the Y-chromosome
The good news is we know of two rodent lineages that have already lost their Y chromosome – and are still surviving.
Both the mole voles from eastern Europe and Japan’s spiny rats have species where the Y and SRY chromosomes have disappeared completely. The X-chromosome, which is found in one or two doses in both sexes, remains.
However, it is not clear exactly how the mole-voles determine sex. Without the SRY Gene, a team led by Hokkaido University biologist Asato Kuroiwa has had more luck with the spiny rat – a group of three species on different Japanese islands, all endangered.
Kuroiwa’s research team found that most genes on the Y chromosome of spiny rats were relocated to other chromosomes. However, she did not discover any sign of SRY nor the gene that can substitute for it.
They have finally achieved their goal. Published a successful identification PNAS. The sequences were found in the genomes of males and not females. After reworking these, the team tested each individual rat for the sequence.
They discovered a small difference at the SOX9 key sex gene on chromosome 3. All males had a small duplication (17,000 base pairs from more than 3 billion), and there was no evidence for it in females.
This tiny bit of duplicated DNA could contain the switch that normally activates SOX9 in response SRY, they suggest. They found that the duplication increased SOX9 activity in mice and this could be a way for SOX9 to function without SRY.
This means that the future of men is in jeopardy
The imminent – evolutionarily speaking – disappearance of the human Y chromosome has elicited speculation about our future.
Some lizards, snakes, and other species are exclusively female-only. They can create eggs using their genes via what is called “genes” Parthenogenesis. However, this is impossible in humans or other mammals as there are at least 30 genes “imprinted” that only work if they come directly from the father via his sperm.
The sperm is necessary for reproduction, and the men we need to reproduce are also required. Therefore, the end Y could bring about the end the human race.
The new finding supports an alternative possibility – that humans can evolve a new sex determining gene. Phew!
There are risks associated with the development of a new gene that determines sex. What happens when more than one new system is developed in different parts?
A “war” on sex genes could lead the to the seperation of new species. This is exactly what happened with spiny rats and mole voles.
So, if someone visited Earth in 11 million years, they might find no humans – or several different human species, kept apart by their different sex determination systems.
Jenny Graves, Vice-Chancellor’s Fellow and Distinguished Professor of Genetics La Trobe University
This article has been republished from The ConversationUnder a Creative Commons License Learn more Original article.
