A fine structure map of spontaneous and induced mutations in the lambda repressor gene, including insertions of IS elements

Mol Gen Genet. 1981;184(3):364-71. doi: 10.1007/BF00352506.


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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacteriophage lambda / genetics*
  • DNA Transposable Elements*
  • Escherichia coli / genetics*
  • Genes*
  • Genotype
  • Mutation*
  • Repressor Proteins / genetics*
  • Species Specificity
  • Transcription Factors / genetics*


  • DNA Transposable Elements
  • Repressor Proteins
  • Transcription Factors