Fig. 1. Structural characteristics of the butyrylcholinesterase gene. The locations of the three introns and four exons are indicated. The location and direction of the amplification primers for exon 1 (1F and 1R), exon 2A (2F and 2.2R), exon 2B (2.2F and 2R), exon 3 (3F and 3R), and exon 4 (4F and 4R) are indicated by arrows. The white boxes indicate untranslated sequence; the black box is the leader sequence; and the dotted area is the coding region for the mature enzyme. UTR = untranslated region.