title: A fine structure map of spontaneous and induced mutations in the lambda repressor gene, including insertions of IS elements.
abstract: Mutations at over 70 sites in the cI gene have been mapped by 4-factor crosses and assigned precise or approximate positions in the DNA sequence. 16 of 25 spontaneous mutations were insertions of IS1, IS3 or IS5 into AT-rich regions of cI. The 5-methylcytosine in the sequence Cm5CAGG is a hot spot for spontaneous cI amber mutations. Recombination frequencies between mutations were proportional to distance with the exception of amber mutations at 4 sites, including the host spot for spontaneous mutations. Mutations with a given phenotype are clustered on the genetic map. No missense mutations affecting repressor activity were found in the central one-third of cI, but 5 of 6 ind- mutations were located in this region. The amino-terminal third of the gene contains the sites of most trans-dominant cI- mutations, and of all ts mutations that result in repressors that are reversibly inactivated at high temperatures.
mesh_terms: D010582:Bacteriophage lambda / Q000235:genetics*; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000235:genetics*; D005796:Genes; D005838:Genotype; D009154:Mutation; D012097:Repressor Proteins / Q000235:genetics*; D013045:Species Specificity; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D004251:DNA Transposable Elements; D012097:Repressor Proteins; D014157:Transcription Factors