Fig. 2. A single 2.3 kb mRNA is disrupted in ida mutants. (A) A schematic of the 63F genetic locus is presented. The position of three subclones from the 63F walk and dSc2, ida, and mge gene structures are shown. Exons are demarcated by open rectangles, and small arrows mark the direction of transcription. Genomic DNA missing in ida¹⁰⁷ and Df(3L)449 deficiency stocks is indicated by gaps marked with parenthesis. A solid line represents genomic DNA present in the P[w⁺ 63F/k1] transgene (see text for details). The proximal boundary of the P[w⁺ 63F/k1] transgene is off the scale of the figure. (B) Three identical northern blots with samples isolated from homozygous animals of the genotypes indicated were prepared. The probes used are designated above each blot. A strand-specific riboprobe generated against the full-length p63F.15 subclone using T3 polymerase hybridizes to ida and dSc2 transcripts. A riboprobe generated using T7 polymerase recognizes mge. Note that mge and dSc2 transcript levels are unaffected in ida mutants. A blot hybridized for rp49 serves as a loading and blotting control.