The objective of this study is to define the functions involved in recombination reactions that are active in the absence of a functional homologous or generalized recombination (Rec) pathway. Examples of important biological processes that depend on Rec-independent recombination include, integration and excision of prophage as well as translocation of transposable genetic elements such as Insertion Sequences (IS) and antibiotic resistance elements (Tn). The primary approach to this proposal is genetic. We have designed a method that has successfully enabled us to select mutants of Escherichia coli that are defective for the site-specific recombination reaction involved in the integration and excision of bacteriophage lambda. The mutants, him (host integration mediation) show a wide range of effects on phage site-specific recombination, transcription, replication as well as translocation and precise excision of Tn elements. In order to extend these studies, we propose to isolate more mutants using an improved selection system along with variations that should permit selection of a more diverse collection of mutants. In order to use these mutants to define the functions involved in non-Rec recombination, we propose the following studies: 1) Mutations will be mapped and dominance patterns established. 2) The effect on lambda site-specific recombination will be determined. 3) The effect on precise excision and transposition of IS and Tn elements will be determined. 4) Mutations that suppress the effects of him mutations will be isolated and characterized. 5) The effect on the growth of bacteriophage mu will be determined. 6) Any identifiable changes in gene products will be looked for using two dimensional gel electrophoresis. These studies should not only yield information about site-specific recombination of phage lambda as well as translocation of Tn elements, but they should produce information applicable to studies on viral induced malignant transformation.