Carvalho A B, Vaz S C, Klaczko L B
Departamento de Genética, Universidade Federal do Rio de Janeiro, Brazil.
Genetics. 1997 Jul;146(3):891-902. doi: 10.1093/genetics/146.3.891.
In several Drosophila species there is a trait known as "sex-ratio": males carrying certain X chromosomes (called "SR") produce female biased progenies due to X-Y meiotic drive. In Drosophila mediopunctata this trait has a variable expression due to Y-linked suppressors of sex-ratio expression, among other factors. There are tow types of Y chromosomes (suppressor and nonsuppressor) and two types of SR chromosomes (suppressible and unsuppressible). Sex-ratio expression is suppressed in males with the SRsuppressible/Ysuppressor genotype, whereas the remaining three genotypes produce female biased progenies. Now we have found that approximately 10-20% of the Y chromosomes from two natural populations 1500 km apart are suppressors of sex-ratio expression. Preliminary estimates indicate that Ysuppressor has a meiotic drive advantage of 6% over Ynonsuppressor. This Y polymorphism for a nonneutral trait is unexpected under current population genetics theory. We propose that this polymorphism is stabilized by an equilibrium between meiotic drive and natural selection, resulting from interactions in the population dynamics of X and Y alleles. Numerical simulations showed that this mechanism may stabilize nonneutral Y polymorphisms such as we have found in D. mediopunctata.
在几种果蝇物种中，存在一种名为“性比”的性状：携带某些X染色体（称为“SR”）的雄性由于X - Y减数分裂驱动而产生偏雌性的后代。在果蝇中，由于Y连锁的性比表达抑制因子等因素，这种性状具有可变的表达。有两种类型的Y染色体（抑制型和非抑制型）和两种类型的SR染色体（可抑制型和不可抑制型）。性比表达在具有SR可抑制型/Y抑制型基因型的雄性中受到抑制，而其余三种基因型则产生偏雌性的后代。现在我们发现，来自相距1500公里的两个自然种群的Y染色体中，约10 - 20%是性比表达的抑制因子。初步估计表明，Y抑制型在减数分裂驱动方面比Y非抑制型具有6%的优势。这种非中性性状的Y多态性在当前的群体遗传学理论下是出乎意料的。我们提出，这种多态性是由减数分裂驱动和自然选择之间的平衡所稳定的，这是由X和Y等位基因群体动态中的相互作用导致的。数值模拟表明，这种机制可能会稳定我们在果蝇中发现的非中性Y多态性。
