Genomic locations of the 51 potential Drosophilaodorant-binding protein genes. The location of each of the 51Obp genes is indicated by a horizontal line. Chromosomal arms are scaled as in Rubin et al. (2000). Conserved intron insertion sites (cf. Fig. 2) are given in parentheses; for clarity of presentation, “2” is used for 2a-c and “5” for 5a-b. Plus-C and Minus-C subfamily members are identified as in Figure 3. Olfactory system expression (cf. Table 1) is indicated by an asterisk.