Figure 1.—

The cpo locus at 90D on chromosome III. The cpo locus at 90D1-6 is large and complex, spanning >100 kb and encoding three different messages: cpo 61.1 (3.4 kb), cpo 61.2 (2.5 kb), and cpo 17 (3.0 kb). For simplicity, only the transcript corresponding to cDNA 61.1 is shown; the mutations described here apparently affect only this transcript (Bellen et al. 1992b). The exons are represented as numbered boxes. The solid boxes correspond to untranslated exons, while the hatched boxes correspond to protein-coding exons. The relationship of cpo 61.1 to the corresponding nucleotide numbers in genomic scaffold AE003720 (release 3) is indicated below the splicing diagram. All of the alleles examined in this study are P-element insertions in the promoter region of transcript 61.1 just 5′ to exon 1. Interestingly, the cpo alleles EG1, l2, cp1, and cp2 are all inserted at the same site between nucleotides 12297 and 12298 on scaffold AE003720. The v3 allele is a P-element insertion 8 nt 3′ of the other alleles. All of these insertions are positioned between enhancer-like sequences and the transcription start site for cpo 61.1 at 12335 (the transcription start site is indicated as a large boldface A in the expanded portion). This region has been shown to contain most of the key regulatory sequences for cpo expression (Bellen et al. 1992b).