The mapping and characteristics of cI am mutants of gamma will be continued in order to correlate mutations with specific nucleotides in the gene sequence. Phage stocks containing a mutation that increases transcription of cI will be constructed to test the hypothesis that transcription influences the high mismatch repair characteristic of certain amber mutants. In order to compare the polarity of cI am mutants, the synthesis of the product of the adjacent rex gene will be studied. Insertion sequences (IS) in cI map like point mutations, but have characteristic effects on recombination and mismatch repair. Insertions at 8 sites in cI are available for study. The effects of the recombination genes of the host and phage on recombination involving the insertions will be compared.
