Fs(2)Ugr¹ homozygous females have defects in early oogenesis. Fs(2)Ugr¹ mutant follicles at previtellogenic stages often show normal morphology, although some are degenerated. A few mutant follicles do reach the vitellogenic stage 10 but the overall morphology of these appears to be abnormal. Fs(2)Ugr¹ follicles are not able to develop upon maturity and become degenerated into the ovary. A small number of Fs(2)Ugr¹ follicles succeed to choriogenesis. In such follicles many dramatic structural abnormalities can be seen. For example, abnormal chorionic folds protrude into the oocyte and the ooplasm is less dense than in wild-type embryos. There is frequently an incomplete, abnormal and broken egg envelope around the oocyte. There appear to be defects in all eggshell layers except for the exochorion. The vitelline membrane is irregularly shaped and does not surround the oocyte uniformly; in some oocytes it is thinner or thicker than wild type. The innermost chorionic layer is either not observed or it is seen as multiple layers. Additionally, the inner most chorionic layer appears to be absent ot is seen as multiple layers. The endochorion is severely affected; in most cases it is seen as amorphous material.

Heterozygous females arrest the development of the oocyte at stage 10 and do not lay eggs.

Development of the egg primordia proceeds normally up to about stage 10. Subsequently the nurse cell nuclei become pycnotic with heavily condensed chromatin, and the egg primordia degenerate.

dominant female-sterile. Heterozygous females are agametic; germ line independent.