Changes in DNA base sequence induced by gamma-ray mutagenesis of lambda phage and prophage.
Mutations in the cI (repressor) gene were induced by gamma-ray irradiation of lambda phage and of prophage, and 121 mutations were sequenced. Two-thirds of the mutations in irradiated phage assayed in recA host cells (no induction of the SOS response) were G:C to A:T transitions; it is hypothesized that these may arise during DNA replication from adenine mispairing with a cytosine product deaminated by irradiation. For irradiated phage assayed in host cells in which the SOS response had been induced, 85% of the mutations were base substitutions, and in 40 of the 41 base changes, a preexisting base pair had been replaced by an A:T pair; these might come from damaged bases acting as AP (apurinic or apyrimidinic) sites. The remaining mutations were 1 and 2 base deletions. In irradiated prophage, base change mutations involved the substitution of both A:T and of G:C pairs for the preexisting pairs; the substitution of G:C pairs shows that some base substitution mechanism acts on the cell genome but not on the phage. In the irradiated prophage, frameshifts and a significant number of gross rearrangements were also found.
Tindall
K R
KR
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511.
Stein
J
J
Hutchinson
F
F
D010582:Bacteriophage lambda / Q000235:genetics / Q000528:radiation effects*; D001482:Base Composition; D001483:Base Sequence; D004279:DNA, Viral / Q000235:genetics / Q000528:radiation effects*; D004926:Escherichia coli / Q000235:genetics / Q000528:radiation effects; D005720:Gamma Rays; D008969:Molecular Sequence Data; D009154:Mutation; D013014:SOS Response, Genetics / Q000528:radiation effects
D004279:DNA, Viral