Lambda CIN-1, a New Mutation Which Enhances Lysogenization by Bacteriophage Lambda, and the Genetic Structure of the Lambda CY Region

Seven lambda cy mutants have been mapped within a small region located approximately halfway between the rightward boundary of the imm⁴³⁴ region and the lambda cII gene. The seven mutants lie at four sites separated by a total distance of about 12 nucleotide pairs, as estimated from recombination frequencies. Six of the seven mutants lie on the right side of the cy fine structure map, spanning a total distance of about 3–5 nucleotide pairs. Lying approximately 11–21 nucleotide pairs to the left of the leftmost cy mutant is a newly described mutation called cin-1, for c independent. The cin-1 mutation allows some lysogenization when coupled with any cy, cII or cIII mutant, but not when coupled with a defective cI gene. The cin-1 mutation, like cy mutants, has a cis-dominant action upon the cI gene in mixed infections. The observation that λimm⁴³⁴ cin-1 cy2001 lysogenizes efficiently, but not λimm⁴³⁴ cin-1 cy2001 cII68 nor any other λimm⁴³⁴ cin-1 cy derivative, is interpreted to mean that all of the cy mutants on the right side of the cy fine structure map inactivate a binding site for cII/cIII function, but that cy2001, the single mutant on the left side of the cy fine structure map, does not inactivate that binding site.