The long-term goal of my research is to understand regulation of gene expression and genetic recombination in molecular terms. We have selected the temperate bacteriophage lambda as a particularly useful material for this purpose. Four aspects of lambda regulation and recombination are now under study: (1) temporal turn-on control of lambda directed protein synthesis and mRNA production during lytic growth of the virus; (2) repression turn-off control of lambda directed protein synthesis and mRNA production during the lysogenic response to infection; (3) nature and control of the genetic recombination event which inserts the viral DNA into the host DNA in the lysogenic response to infection (integrative recombination); (4) nature and control of the genetic recombination event which occurs between phage DNA molecules during lytic growth (general recombination). We plan to initiate work on another aspect of lambda regulation: control of lambda DNA replication. Our objective is to understand these processes at a biochemical level by characterizing each in a purified system (e.g. lambda DNA, RNA polymerase, plus purified repressors for case (2); lambda DNA plus purified recombination enzymes for case (4)).