FIG. 2.

Molecular analysis of bl. (A) Map of the bl genomic region. Restriction sites are represented by vertical bars, EcoRI sites above and XbaI sites below. Breakpoints or deletions found in bl alleles are indicated by shaded boxes. The location and polarity of the insertion were determined by Southern blot and sequence analysis (data not shown). Genomic λ phages are indicated. The triangle indicates the P-element insertion site. (B) Northern blot analysis revealing bl transcripts, using CR22 cDNA as a probe. mRNAs of 1.9 and 2.1 kb are detected during the first 10 h of embryogenesis (0 to 5 h, lane 1; 5 to 10 h, lane 2); only the larger transcript is detected in the later stages of embryogenesis (lane 3), in third-instar larvae (lane 4), and in adult females (lane 5). Each lane contains 5 μg of poly(A)⁺ mRNA.