Figure 6.—

Model for the movement of Dbp80 and RpL15 throughout the genus Drosophila. At least two interelement movements must have taken place to explain the present locations of these genes in Drosophila. Evidence for the location of Dbp80 relative to RpL15 is lacking for the common ancestor of the genus Drosophila, so two hypotheses for the first relocation can be considered. Either both genes were located on separate elements in the common ancestor (H1) and Dbp80 moved adjacent to RpL15 in the common ancestor of the subgenus Sophophora, or the genes were adjacent (H₂) and Dbp80 moved away from RpL15 in the subgenus Drosophila consistent with the position in the genome of D. virilis. Further relocation events take place in the subgenus Sophophora. The ancestral location of RpL15 in this subgenus is apparently centromeric, but it has moved to the middle of element E in D. pseudoobscura, possibly defining a region of intercalary heterochromatin. Following the fusion of elements D and E in the melanogaster lineage, the region containing RpL15 and Dbp80 moved between these elements by a pericentric inversion.