Fig. 2. Molecular characterization of drm. (A) Physical map between male-specific lethal-2 (msl-2) and foraging (for) (cytological regions 23F3 to 24A3). Genomic DNA in P1 phage clones DS01379 and DS01340 is shown above the map, with the 18.1 kb fragment used for genomic rescue experiments shaded in gray. Characterized genes are shown with arrows representing their directions of transcription, as annotated in GadFly (Rubin et al., 2000b). The l(2)k10101 P element, mobilized to generate deficiency alleles, is represented by an inverted triangle. Below, deficiencies are represented by open bars with breakpoint uncertainties shown in gray. Df(2L)tim⁰² and Df(2L)ed¹ were used for rough mapping of the drm¹ allele. The breakpoints of Df(2L)drm^P1 and Df(2L)drm^P2 were mapped molecularly. B, BamHI. (B) Expanded view of the 11.9 kb BamHI fragment that includes the drm gene. The I element in the drm¹ chromosome is inserted 35 bp upstream of the transcription start site. The drm transcription unit is 8.5 kb with three exons spliced together to form a 2.5 kb mRNA. An alternate first exon (1') was found in 10% of 5' RACE products, and several alternate transcriptional stop sites (dotted lines in exon 3) were present in 3' RACE products. The drm ORF (black) spans the second splice junction. (C) Northern blot of 50 µg total embryonic RNA (0-17 hours) and 1 µg poly(A) RNA shows the approximately 2.5 kb drm mRNA. (D) Schematic representation of the Drm protein folded to form one C₂H₂ and one C₂HC zinc finger. Residues conserved in the canonical C₂H₂ zinc finger are shaded gray and residues altered in the drm point mutants are black (see Table 1).

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