Immunohistochemistry using anti-FRU^M was performed to assess expression of the male forms of FRU protein in the CNSs of 2-d-old male pupae from a wild-type (WT) stock, afru³ -bearing strain, and pupal progeny resulting from crosses of fru-breakpoint variants to each other or certain such variants to fru³ (the only homozygous-viable mutant used here). The w-including genotypes are chromosome aberrations, each involving a breakpoint within the fru locus; most of the Df-including genotypes are deletions, each of which has one breakpoint at this locus and thus is missing part of the locus (Df-fru^w24 removes the entire locus). Nearly all breakpoint combinations, with respect to the chromosome aberrations depicted in Figure 1, were generated, except forfru^w24/Df-Cha^M5 (which die as embryos). For the results column, the wild-type staining level was simply set at 100, because there was no apparent FRU^Mimmunostaining in pupae carrying any of these mutant orfru-breakpoint variant specimens.