300 million years ago, there was no Y-chromosome, and gender was only determined by the physical environment, like, temperature; however, one day, a genetic mutation happened on one X-chromosome in a primitive mammal, which was the birth of SRY. And, as we now know it, that X-chromosome with SRY is now called Y-chromosome.
However, Y-chromosome is still too young, 300 million year’s time is still not enough for full stabilization. For unknown reasons, X and Y-chromosome keep conflicting with each other, and the result is the genes in Y-chromosome have decreased from 1400 at first to only dozens right now.
What a horrible story! Scientists began to worry about the future of Y-chromosome, which also brings out a rather important problem: Will males disappear?!
But then the story takes an unexpected turn.
The study of Diego Cortez, from Swiss Institute of Bioinformatics and his team demonstrated that Y-chromosome’s gene loss disappeared approximately 2500 years ago, while the genes that are left might possess great powers stabilized genetic formulas.
As is known to all, other chromosomes all have the ability of recombination and crossover with their ‘twin siblings’, while Y-chromosome can only repair and be saved on both sides only through its corresponding X-chromosome. Another question thus arises again, how does it do that?
Although Y-chromosome is the smallest chromosome in our body, figuring out its content is definitely not a piece of cake. In the initial stage of HGP (Human Genome Project), it really sounded insane to identify what exactly the gene was in the intermediate range – mostly due to the fact that there were too many duplicated genes and inert genes (no physiological function) there. An expert from this field used to pose an example‘Analyzing genes in Y-chromosome is like walking into a room built by mirrors – one cannot even tell ceiling and floor apart.’
Not until 2003 did scientists figure out the secret of the ‘mirror’- it is actually the palindrome structure of the genetic code. For example, ABCDEFG and GFEDCBA just form a palindrome structure, which is also known as a mirror image. The former troublesome mirror has now become the key to the investigation of Y-chromosome. Subsequently, scientists found it is this‘mirror’ that prevents Y-chromosome from degeneration. Palindrome structure helps Y-chromosome to bend from the middle range, which makes recombination and crossover possible. It also plays the role of backups by repairing the mutation from the opposite one. Scientists believe the dozens of genes left in Y-chromosome will remain stable for a long period time.
The research on Y-chromosome has never ceased. STRtyper-27Y multiplex PCR florescence test kit developed by Health Gene Tech is mainly used on paternal genetic test. It increases the identification resolution from males of kin. Not only does the optimized reaction system decreases the amplification time, but also the period of validity becomes much longer.
- Charlesworth, B. & Charlesworth, D. Trans. R. Soc. Lond. B 355, 1563-1572 (2000).
- Bachtrog,D.Nature Rev.Genet.14,113-124(2013).