In situ hybridization of nuclear and cytoplasmic RNA to locus 2-48BC in Drosophila hydei.

The maximum grain density over the "heat-shock" locus 2-48BC of Drosophila hydei polytene chromosomes obtained after in situ hybridization of nuclear RNA extracted from tissue culture cells labelled during incubation at 37 degrees C is five times higher than that obtainable by using polysomal RNA isolated from the same cells. Furthermore, the addition of a large excess of unlabelled polysomal RNA reduced the amount of in situ hybridization of nuclear RNA by only 20% showing that nuclear 2-48BC RNA contains sequences not present in polysomal 2-48BC RNA.--The polysomal 2-48BC RNA is polyadenylated, as are the RNA sequences present in the polysomes complementary to the other two major "heat shock" loci 2-32A and 2-36A. Polyadenylated RNA, with an apparent size of 15S, complementary to locus 2-48BC is also found in the cytoplasm of D. hydei salivary glands.