We are currently involved in three lines of experimentation that deal with DNA replication and recombination. 1. The first line of experimentation deals with the isolation and characterization of the DNA recognition element(s) which serve as the origin for negative strand synthesis in the viruses G4, St-1, alpha 3, and phiK. The de novo synthesis of these virus negative strands is, in many ways, analogous to formation of an Okazaki fragment. 2. A second line of experimentation involves the isolation of the rolling circle/phage-capsid complex, which is the actively replicating DNA molecule in the phiX-174 late life cycle. 3. Thirdly, we are using the electron microscope and in vivo and in vitro studies to explore the process of DNA recombination. We can observe and analyze intermediates in the recombination process. Current experiments deal mainly with the development of an in vitro system for studying the enzymology of generalized recombination.