Mutations affecting genetic recombination in bacteriophage T4D: I. Pathways analysis

Abstract

The nature of DNA synthesis and recombination has been examined in bacteriophage T4D mutants deficient in recombination and repair. The interactions of several of these mutations have been assessed by measuring DNA synthesis, uv sensitivity, and genetic recombination in multiply mutant strains. Certain multiple mutants exhibited a 60-fold reduction in recombination frequency. Gene x- and gene y-deficient strains each exhibited an arrest in DNA synthesis and a concomitant interruption of concatemer formation as measured by alkaline sucrose density gradient centrifugation. The arrest in DNA synthesis was suppressed by the presence of a second mutation in gene 55. Strains carrying x and y mutations failed to complement mutants fdsA and fdsB, respectively. A gene w mutation was found to suppress the arrest in DNA synthesis caused by mutations in genes 46–47 and in gene 59. In the case of genes 46–47, genetic recombination was not restored, while for gene 59 mutants genetic recombination and uv resistance were partially restored. A gene w mutation did not suppress the DNA arrest phenotype produced by mutations in the x or y genes. The T4B strain 1206 was found to contain a mutation in gene w, along with several uncharacterized mutations.