Studies on the sterility phenotype of the pleiotropic mutant fused of Drosophila melanogaster

A further description of the sterility phenotype for three different alleles of the female‐sterile mutant fused of Drosophila melanogaster is reported. It was found that: No more than 35% of the eggs laid by females homozygous for fu, fu57a, and fu59 when mated to Oregon R males are capable of hatching into larvae. This percentage is unaffected by the presence of a Y chromosome in the mother. The data indicate that the mechanism of control in the activation of the wild type allele of fused in an embryo from a homozygous fused mother is imprecise. Homozygous fu, fu57a, and fu59 females show apparently allelic differences in the number of eggs they are capable of laying. Heterozygous fu59 females have a somewhat reduced egg laying capacity when compared to Oregon R females if they are the daughters of either homozygous or heterozygous fu59 mothers but show no such difference if they are the daughters of Oregon R mothers. These data are consistent with the idea that fused is hypomorphic.