Do we really need the chromosome Y ?

Do we really need the chromosome Y ?

In humans , sex is determined by two chromosomes X and Y. A pair of X gives daughter X and Y a boy. But , while the X carries several hundred genes useful in other compartments of the body that the genital system , the Y- rich is far less . He lost many genes since its appearance in the world of the living , and even if this degeneration seems stopped for about 25 million years , the Y chromosome gives the impression of being curled , concentrated on his " heart of business " , namely to determine the male and manufacture sperm. Hence the question posed some geneticists : How many genes are needed for this double task?

If you believe a U.S. study published by Science on November 21 , the correct answer , at least in mice, is the minimum response : two missions, two genes. The team from the University of Hawaii who wrote this article has used the architect Sry that in utero triggers differentiation of the embryo by directing its gonads during manufacturing towards testicular gene. Simply, these researchers knew it needed add at least another gene because even male appearance , individuals thus obtained would be sterile , sperm production is incomplete home. They therefore have the added Eif2s3y gene in mice , the process unlocks spermatogenesis .




The result was not perfect. Mice obtained , some differences remained in the testes compared to normal mice , and especially making gametes did not go to completion. She stopped at the stage of spermatids , which precedes the sperm . These mice therefore could not have children. Never mind , researchers have said , would it be possible, using a technique of in vitro fertilization , to give a helping hand to nature and to obtain offspring by implanting these spermatids in eggs? The response was positive . The resulting mice were healthy and , once adult , fertile . In absolute terms, only two genes of the Y chromosome are therefore sufficient to create the male.

Although the authors caution that this result can not be directly transposed to Homo sapiens , which is not Eif2s3y gene, it opens an interesting line of thought about what , biologically , masculinity . The last paragraph of the Science study indeed begins with this sentence: " Considering that we got a live offspring using germ cells ( cells that are likely to produce gametes , Ed) with only two genes Y chromosome, one can question the importance of the Y chromosome in male reproduction . " To put it frankly, the question is : Has anyone really need the Y chromosome ?

Warning: the question does not mean that it can happen to men the natural fertilization of ovules, but that men could possibly happen in this small chromosome , which so far was the brand manufactures genetic male . The study notes that , in mice and humans , a little more than two genes are probably essential to achieve good breeding males. But nothing ultimately obliges these genes remain where they are to work! The animal world is also rich in species whose males do not over or Y chromosome and are doing very well with an X chromosome ( in the case of grasshoppers, crickets and cockroaches ) .

As explained Monika Ward, who led the study, the ScienceBlog website , " it might be possible to eliminate the Y chromosome of the mouse in its entirety if the two genes were installed at appropriate locations ." It is also conceivable to play their role to others. The researcher has explained to Nature she was currently working on the identification, on other chromosomes , genes that interact with those of Y. The idea is to activate these genes, " partners " so that they take over their colleagues and thus , ultimately, to send the Y chromosome in the dustbin of evolution ...

Pierre Barthélémy ( follow me on Twitter here or on Facebook here )