Genetic and physical methods will be used to determine the structures of the primary products of bacteriophage lambda recombination in order to define and distinguish the roles of bacterial and phage recombination functions. The function(s) responsible for adenine methylation independent mismatch will be characterized. The structures of lysogenic integration of Mu and the products of abortive Mu infection in him strains of E. coli will be characterized. An assay for in vivo inverted dimer formation arising from double strand breaks in the DNA of S. cerevisiae will be devised in order to identify and characterize the functions responsible for this fusion transaction.