The project described in this proposal has as its aim an understanding of the genetic structure of the alpha-glycerophosphate dehydrogenase (alpha GPDH) locus in Drosophila melanogaster. Proper function of this gene product is essential for a normal life span in D. melanogaster. We hope to elucidate the ways in which the action of the gene is controlled in order to better understand the metabolic pertubations which lead to senescence. Null activity mutations will be induced and recovered with devices which separate individuals on the basis of flightlessness. These null mutants which make incomplete alpha GPDH polypeptide chains will be identified by means of an I125 based radioimmune assay. Following a fine structure genetic analysis which will employ both flanking lethals and the flight separator, these null mutations (putative nonsense mutants) will be localized within the alpha GPDH structural gene. Putative missense mutations, which specify complete alpha GPDH polypeptide chains, will then be positioned in the fine structure map. The map and the mutant polypeptide will be compared with the amino acid sequence of the protein (being determined in the laboratory of Richard Lewontin) and the nucleotide sequences of both coding and non-coding sections of the gene (which will be determined by David Sullivan). These comparisons will allow us to define the locus with regard to its structural and putative regulatory components as well as identify the exact mutational change in several of the null mutants. Several nonsense mutant strains will be subjected to mutagenesis and revertants of the flightlessness phenotype will be recovered. Genetic and biochemical analyses will be made on the revertants to identify suppressors of the nonsense mutations. The post translational mutant suppressors, which will also be identified, will be analyzed for their effects on the life span of two kinds of flies, those deficient and those wild type for alpha GPDH activity.