Recombination between the two progenitor insertions has resulted in the deletion of the genomic sequence between them.
Spermiogenesis is severely disorganised in Df(2L)ΔMst35B/Df(2L)FDD-0338164 males. Many elongating spermatids have abnormal nuclear morphology (nuclei appear bent, with the anterior tip sometimes folded into a hook-like structure) and a large proportion of mutant spermatid nuclei are scattered along the cysts instead of being tightly grouped in bundles of 64 nuclei.
Prtl99C942.T:Avic\GFP-EGFP fails to rescue misshapen sperm heads in Df(2L)FDD-0338164/Df(2L)FDD-0338164 mutants. Df(2L)FDD-0338164/Df(2L)FDD-0338164 mutants have slightly elongated nucleus area (in spermatids during individualization as well as mature sperm) compared to controls.
Mutant males are fertile but produce a variable number of offspring ranging from 50-100% of the number produced by wild-type males. A large proportion of spermatids in the mutant males individualise and nuclear shaping takes place as in wild type. However, approximately 20% of the mutant sperm heads are slim but bent or crumpled. The chromatin is often concentrated at one end of the spermatid head in mutant males. All 64 spermatids in one cyst show the same either defective or wild-type phenotype.
Mutant sperm are more sensitive to X rays than wild type; irradiated mutant males show a higher frequency of induced lethal mutations than control males in a Muller5 test.