Sites of the 5S ribosomal genes in Drosophila. I. The multiple clusters in the virilis group.

Drosophila melanogaster 125I-5S RNA was annealed to salivary gland preparations of 6 species in the virilis group of Drosophila. Two patterns of annealing were found. D. virilis, D. montana and D. borealis showed three 5S gene clusters on chromosome 5; Sd-f and Wc-j were strongly labeled, but Xa-e was weakly labeled. D. montana and D. borealis have a greater percentage of their total 5S cistroms at S d-f than does D. virilis. D. americana americana, D. americana texana and D. novamexicana showed 2 sites labeled; no label was seen at Sd-f while Wc-j was weakly labeled and Xa-e was strongly labeled, the reciprocal of the previous pattern in the W-X region. Hybrids between D. a americana and D. virilis showed no difference in chromosome banding at the sites of the 5S clusters despite their pattern difference. D. a texana X D. virilis, on the other hand, did show a difference in staining the Xa-e region. These patterns fall squarely into the biosystematic groupings deduced by many previous workers.