Strong phenotype. Oocytes produced by homozygous females contain fewer proteinaceous yolk spheres than oocytes produced by wild-type females. These abnormal yolk spheres do contain some yolk. The adult hemolymph of homozygous females contains a much higher level of vitellogenin than normal.

female-sterile affects late oogenesis. Eggs of mutants lack proteinaceous yolk and collapse; ultrastructurally abnormal chorion at anterior end and especially at base of respiratory filaments. No abnormality detectable in chorion protein synthesis. Uptake of the three yolk proteins by yl oocytes is severely reduced, although the proteins accumulate in the hemolymph.