Utilizing the unique genetic flexibility of the fruit fly, Drosophila melanogaster, we intend to probe by means of genetic analysis and the technology of molecular biology the function and structure of two groups of redundant genes in this organism. Specifically, we will be concerned with the ribosomal RNA genes (rDNA) and the S5 RNA genes (5S DNA). Our proposed research can be divided into two major aspects. First, we intend to search for mutations that regulate the expression of the 5S DNA. These experiments involve mutagenesis, genetic analysis and biochemical and genetic characterization of 5S DNA mutants. Second, we intend to construct physical maps of 5S and rDNA. We also intend to determine if the size of the rDNA spacer region is altered after several alternating rDNA magnification and reduction events. These structural studies should provide some insight as to the functional significance of spacer DNA in the eukaryotic genome. BIBLIOGRAPHIC REFERENCES: Procunier, J.D. and Tartof, K.D. Genetic analysis of the S5 RNA genes in Drosophila melanogaster. Genetics 81: 515-523, 1975. Tartof, K.D. Redundant genes. Ann. Rev. Genet. 9: 355-385, 1975.