3D-06 Genetic and phenotypic analyses of a sex-ratio segregation distortion mutation, excess-of-female (exf) in Drosophila simulans

excess-of-female (exf) is a female-biased sex-ratio mutation of Drosophila simulans that has been isolated from a natural population in Japan. exf males produce typically 4-20 times less male progeny than female progeny. Unlike the well-known sex-ratio driver in this species, namely paternal-sonless or sex-ratio, carried by X chromosomes, exf has been found to be autosomal recessive. Aiming to identify, clone and characterize the exf gene, we are currently trying to achieve precise mapping of exf. For this purpose, we have adopted use of SNP markers in combination with visible markers. So far, exf has been mapped midway between e and p, slightly nearer to the latter, on the third chromosome. Moreover, to gain insights into the nature of exf, we are analyzing the exf phenotype under various genetic and environmental conditions. The results suggest that the expressivity of exf is dependent on the genetic background, particularly variety of the X chromosome, and that exf affects spermatids carrying the Y chromosome, irrespective of absence or existence of the X chromosome.