Localization of 5S RNA genes on Drosophila chromosomes by RNA-DNA hybridization

[(3)H]RNA with a high specific activity was prepared from larvae of Drosophila melanogaster grown 4 days in contact with [(3)H]uridine. Purified tritiated 5S RNA was annealed to the DNA of polytene chromosomes, which had been denatured in formamide. The 5S RNA genes are placed within the region 56E-F of the right arm of chromosome 2. This localization was determined from autoradiographs, where the radioactivity from hybrids of [(3)H]RNA and DNA was confined to the 56E-F segment.