mutation frequency responses produced by ultraviolet light are compared in 4 closely related strains of e. coli b/r having the same tyr ( oc ) allele and different excision-repair capabilities : uvr+ ( excision repair initiated by wild-type uvrabc activity ) , uvra ( excision repair defective ) , uvra/pdenv-7 ( excision repair initiated by endonuclease v of bacteriophage t4 , denv activity ) , and uvr+/pdenv-7 ( excision repair initiated by uvrabc and denv activities ) .
C1412791
oc
C0043240
repair