Fig. 9. D. melanogaster OBP homologues. (A) Physical positions of OBP (L1-L12) and DOR loci on chromosomes 1-3 (C1-C3). Numbers are in megabase units (MB); circles mark positions of centromeres. DORs are those identified by the Drosophila Odorant Receptor Nomenclature Committee (2000) and Leslie Voshall (67d; personal communication). Mid-point nucleotide positions of genes were determined using the NCBI Entrez genome server. (B) Spatial organization of genes at loci 2, 6, 10 and 12; based on gene scaffold annotations. Positions of all annotated genes within these regions are shown. Tall boxes are OBP genes (CG numbers) and short boxes intervening genes; exons are indicated only for OBPs, and arrows indicate orientations of OBP genes. Numbers indicate the nucleotide range of each diagram; diagrams of loci 6 and 12 are scaled (1:20, 1:10) relative to those of loci 2 and 10. Locus 7 is not illustrated; two OBP genes are separated by about 44 kbp with six unrelated annotated genes situated between. mtr, mitochondrial thioredoxin (CG8517); OR56a, olfactory receptor.