How do males live without a Y chromosome
And without the Y-chromosome, you can remain a male
In mammals, the sex depends on which sex chromosomes the embryo receives during fertilization: if both of them are X, a "girl" will turn out, if one chromosome is Y, a "boy" will turn out. There is a SRY gene on the Y chromosome, which, interacting with genes on other chromosomes, triggers the male type of development. It seems logical that if there is no Y chromosome, then there will be no "boy" - there is no SRY gene. But, as Tsar Berendeev says in the fairy tale A.N. Ostrovsky's "Snow Maiden", "mighty nature is full of wonders": on one of the Ryukyu Islands there lives a Ryukian spiny mouse, males and females of which have the same number of chromosomes, while males have no Y chromosome - and at the same time they remain males.
The Ryuk mouse (Tokudaia osimensis). Photo from Hokkaido University press release
How to be a male without the Y chromosome – VM
A related species, the Tokunoshima Island spiny mouse (Tokudaia tokunoshimensi), has the same story.
Japanese researchers have been trying to solve the riddle of "non-game" rodents for quite some time, and in a new article Scientific Reports Molecular mechanism of male differentiation is preserved in the SRY-absent mammal, Tokudaia osimensis Tomofumi Otake and Asato Kuroiwa write that, despite the absence of the SRY gene, the same genes of male development are activated in male spiny mice, as if SRY were in place. That is, nothing fundamentally new from a molecular genetic point of view is happening here, the development scheme has remained the same, only it is apparently triggered by some other gene that has taken over the functions of SRY and somehow turns on itself in those individuals who then become males.
It is known that in mammals in general and in primates in particular, the Y chromosome has noticeably decreased during evolution, although complete disappearance is unlikely to threaten it. But even if the male "y" is destined to disappear, it is unlikely that this will mean the disappearance of men – we must think, as in the case of the Ryuk mouse, evolution will find a way to preserve the "stronger sex".
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17.10.2016