| Abstract: | The mutagenic local effect of tritium decay at the 5 position of cytosine in DNA of Escherichia coli was determined in wild-type and in ung strains defective in uracil-DNA glycosylase. In the absence of this in vivo activity any genetic consequences of uracil residues formed in DNA should be enhanced. However, the mutation frequency response was no greater in the mutant strain than in the wild type. This finding is inconsistent with the earlier suggestion that efficient production of C to T transitions by the local effect of 5-3H]cytosine decay results from the formation of uracil in cellular DNA. Some other intermediate should be considered, one that is not a substrate for uracil-DNA glycosylase. |
