Genetic studies of the lac repressor

Abstract

The complete results of the analysis of over 5300 independently derived nonsense mutations in the lacI gene are presented. These have been mapped and divided into specific sites. A total of 105 nonsense mutations derived from 90 different codons can be distinguished, of which several are the result of tandem double base changes induced by ultraviolet light. With the aid of results determined in a preceding paper (Miller et al., 1977), the majority of these mutations have been assigned to points in the gene coding for specific residues in the lac repressor. This allows a detailed correlation of the physical and genetic map. Recombination studies have been carried out using mutations at known sites. For crosses involving mutations separated by less than 30 nucleotides (the main object of this study), a significant lack of agreement between distance and recombination frequency has been found.