Fig. 2. hop mutant ovaries contain fused egg chambers. Heteroallelic combinations of hop alleles show a range of severity of ovarian defects. (A-C) In comparison with wild type (A), loss of hop function results in chambers with additional germ cells, with penetrance and severity determined by allelic combination. Moderate allele combinations, such as hop^msv/hop^GA32 (B), show frequent compound chambers. Severe allele combinations, such as hop^msv/hop^M38 (C), result in extensive fusion of chambers, with no distinct, separated cysts. Orb antibody staining shows that the additional germ cells are the results of multiple germline cysts encapsulated within a single follicular epithelium. In wild-type ovarioles (D), Orb protein is dispersed throughout the germ cells of cysts within the germarium, but is concentrated in the oocyte of chambers in the vitellarium (Orb in red, DAPI in blue). In hop^msv/hop^GA32 ovarioles (E), fused chambers contain multiple germline cysts (arrows), each with its own oocyte. Moreover, a chamber containing 4 fused cysts (F) has 60 ring canals (Kelch staining in red). The multiples of 15 ring canals (F', red) are consistent with chamber fusions rather than extra rounds of germline proliferation.