We are attempting to determine the pattern of RNA transcription adjacent to structural genes in Drosophila melanogaster. Following temperature elevation, only a small number of genes are active. We have isolated messenger RNA produced by Drosophila tissue culture cells at elevated temperatures. This is being used to select bacterial plasmids containing Drosophila heat shock genes and adjacent DNA sequences. Restriction enzymes will be prepared of the Drosophila insertions in the plasmids. We will then attempt to determine which restriction fragments are able to bind radioactive RNA produced by tissue culture cells at various times after temperature elevation. Using this approach, we would hope to determine the distribution of promoters along the DNA of a single chromomere and the possible involvement of long transcription tracts. A second project under this grant is aimed at testing the possiblity that transcription of genetic elements too small to be observed by conventional cytogenetic methods may play an important role in evolution and possibly development. We are testing this possibility by examining the spectrum of fragment sizes in restriction digests of DNA from various species of Drosophila and from Drosophila melanogaster at various developmental stages. The location of specific sequences on gel electrophoretograms of such digests is being done by the method of Southern (1975), using various cloned Drosophila DNA segments as probes. BIBLIOGRAPHIC REFERENCE: McKenzie, S., S. Henikoff, and M. Meselson (1975), "Localization of RNA from heat-induced polysomes at puff sites in Drosophila melanogaster," Proc. Nat. Acad. Sci., USA 72(3):1117-1121.