Fig. 4. Increased doses of da⁺ produce a gain-of-function phenotype. (A-D) Ovarioles stained with the nuclear dye DAPI; (E-H) ovarioles double stained for Vasa (germline, red) and Hts (adducin, present in somatic cytoskeleton and germline spectrosome and fusome, green). (A) Wild-type ovariole. (B) Ovarioles from flies with three copies of da⁺ contain abnormally long interfollicular stalks (arrows). The genotype of the ovariole shown here included a tandem duplication of da⁺ (da⁺/Dp(2;2)da⁺); similar morphology was observed when the extra da⁺ copy was provided by a transposition, carried on the Y chromosome (not shown). (C-E) Ovaries of homozygous da^lyh flies, carrying a duplication of da⁺ on the Y chromosome, exhibit a more extreme phenotype. In these ovarioles, smaller germaria are attached directly to maturing follicles. (E) The staining for Vasa and Hts highlights the gap in follicle stages that is observed between germline in the germarium and the closest individual follicle. (F) These defects are also seen in flies homozgyous for da^lyh with two copies of a heat-inducible da⁺ transgene at 32°C. (G) Likewise, the defects are phenocopied by 37°C pulses of the heat-inducible da⁺ transgenes in a wild-type background. (H) These defects are not seen in wild-type flies exposed to the same heat shock regimen. In each panel anterior is at the top (C,E-H) or towards the left (A,B,D).

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