Mapping missense and nonsense mutations in genecI of bacteriophage lambda: Marker effects

Abstract

Amber and missense mutations in genecI of bacteriophage lambda were mapped by reciprocal four-factor crosses, selecting recombinants between the outside markers (N amber andO amber). Distances betweencI missense mutations were additive. SeveralcIamber mutants recombined with othercI mutations with a higher-frequency than expected from the map location. Multiple exchanges in theN-O region occurred at a frequency greater than expected by chance. This “high negative interference” was especially marked in crosses with thecIamber mutations that were strong recombiners. A newind mutation,ind2, was found neartsU51, to the left of the previously-knownindl mutation, which is located almost in the center of genecI. The mutationc50 maps to the right oftsU50 andc71. Mutationsc60, andts71, which differ in phenotype, are apparently at the same site.