Fig. 4: Retained introns share conserved sequence properties.

a–d Comparison of donor and acceptor sequences of spliced and retained introns. The structure of the dsx gene including introns (black lines), the retained intron for dsx^M2 (thick green line), and exons (boxes), as well as splicing donor and acceptor sequences for each intron in D. melanogaster (a), D. simulans (b), D. mojavensis (c) and D. virilis (d). Introns were labeled with numbers followed by “f” (female-specific splicing) or “m” (male-specific splicing). respectively. As for the consensus sequences, Y indicates pyrimidine, and N indicates either A, G, T or C. The number of pyrimidines in the 12 upstream nucleotides of the acceptor sequence NYAG is indicated in the brackets for each intron. e Comparison of retained intron sequences of dsx^M2 in four Drosophila species. Underlined letters indicate potential Tra binding sites. Black asterisks indicate perfect matches of amino acids among four species, and gray asterisks indicate three matches out of four species.