Fig. 4. Northern blot analysis of wild-type toy and ey mRNAs and of toy^hdl mRNAs. (A) Developmental profiles of wild-type toy and ey mRNAs. A northern blot of poly(A)⁺ RNA, isolated from wild-type embryos, larvae and pupae of the stages indicated, and from female and male adults, was analyzed by autoradiography after successive hybridizations with ³²P-labeled 1.73 kb toy cDNA (top), 2.2 kb 1-tubulin genomic DNA for reference (bottom; Theurkauf et al., 1986), and 2.85 kb ey cDNA (middle). Sizes of mRNAs were calibrated with the same markers shown in B. (B) Northern blot analysis of toy^hdl mRNAs. A northern blot of poly(A)⁺ RNA, isolated from adult flies (raised at 19°C) of the genotype indicated, was analyzed as described in A. Putative poly(A) addition signals consistent with the wild-type (wt) and toy^hdl mRNA sizes observed include the canonical AATAAA at positions 535 and 1633, and the non-canonical CATAAA at position 180 of the last exon of toy (cf. Fig. 3B). Arrows indicate which mutant mRNAs presumably are derived from which wild-type mRNAs by the use of the same poly(A) addition sites. RNA size markers shown were produced by the RiboMark Labeling System (Promega).