The exon/intron structure of the blt gene and Northern blot analysis. (A) Exons: filled squares, introns: lines. (B) Northern blotting revealed a single band (the arrow indicates the 2.37 kb marker size), visualized with digoxigenin-labeled probe, using the total RNA extracted from heads and bodies of male and female flies. Lane 1: female body, lane 2: male body, lanes 3 and 4: their respective heads. The lower panel shows the corresponding ribosomal rp46 mRNA.