Department of Genomics, Faculty of Biotechnology, University of Wrocław, ul. Fryderyka Joliot-Curie 14a, 50-383, Wrocław, Poland.
Sci Rep. 2018 Jun 12;8(1):8978. doi: 10.1038/s41598-018-27219-1.
Sex determination in mammals is strongly linked to sex chromosomes. In most cases, females possess two copies of X chromosome while males have one X and one Y chromosome. It is assumed that these chromosomes originated from a pair of homologous autosomes, which diverged when recombination between them was suppressed. However, it is still debated why the sex chromosomes stopped recombining and how this process spread out over most part of the chromosomes. To study this problem, we developed a simulation model, in which the recombination rate between the sex chromosomes can freely evolve. We found that the suppression of recombination between the X and Y is spontaneous and proceeds very quickly during the evolution of population, which leads to the degeneration of the Y in males. Interestingly, the degeneration happens only when mating pairs are unfaithful. This evolutionary strategy purifies the X chromosome from defective alleles and leads to the larger number of females than males in the population. In consequence, the reproductive potential of the whole population increases. Our results imply that both the suppression of recombination and the degeneration of Y chromosome may be associated with reproductive strategy and favoured in polygamous populations with faithless mating partners.
哺乳动物的性别决定与性染色体密切相关。在大多数情况下，女性拥有两条 X 染色体，而男性则有一条 X 染色体和一条 Y 染色体。人们认为这些染色体起源于一对同源常染色体，当它们之间的重组受到抑制时，这对同源常染色体就会发生分歧。然而，为什么性染色体停止重组以及这个过程是如何在大部分染色体上扩散的，仍然存在争议。为了解决这个问题，我们开发了一个模拟模型，其中性染色体之间的重组率可以自由进化。我们发现，X 和 Y 染色体之间重组的抑制是自发的，并且在种群的进化过程中进行得非常快，这导致了 Y 染色体在雄性中的退化。有趣的是，只有当交配对不忠实时，退化才会发生。这种进化策略从有缺陷的等位基因中清除了 X 染色体，并导致种群中女性数量多于男性。因此，整个种群的繁殖潜力增加了。我们的研究结果表明，重组的抑制和 Y 染色体的退化可能与繁殖策略有关，并在具有不忠实交配伴侣的多配偶种群中受到青睐。
