cDNA screens for specific splice choices of Bru-3. In the diagrams, arrows indicate the position and direction of primers in regard to the exons (e.g., E6, E7, E8 and E9) used for PCR. The expected sizes of PCR products (in nucleotides) are presented below the diagram. In the gel images, fly lines are indicated for each track. The long dash marks the track of a negative control (no template). Sizes of DNA ladder (ML) are shown to the right of the gel image. (A) Screening cDNA pools for the splice variant containing exon 6. The exon was included in mature mRNAs of D. pseudoobscura (pse), D. persimilis (per) and D. virilis (vir), whereas it was absent in D. melanogaster (mel) cDNA pool. (B) Screening cDNA pools for the splice variant containing exon 8. Although exon 8 was included in mature mRNAs of all tested species of the obscura group - D. obscura (obs), D. affinis (aff), D. bifasciata (bif), D. subobscura (sub) - it was not found in cDNA pools of the species outside of the obscura group, in D. melanogaster (mel) and D. virilis (vir).