a1 Department of Biology, State University of New York, New Paltz, New York 12561
5-Bromouracil was shown to enhance the mutation frequency in an ultraviolet sensitive strain of Neurospora crassa (uvs-2) that was previously irradiated with ultraviolet light. The design of the experiment eliminated light or dark repair as possible hypotheses to account for the observed enhancement. Since a similar effect was noted at the rib-1 locus in N. crassa, which is not a UV-sensitive strain, it appears that the error prone repair mechanism in N. crassa may be related to post-replication repair. This enhancement may be attributed to the interference of 5-bromouracil with post-replication repair. It is also postulated that the maximum increase in the mutation frequency occurs when the greatest number of unrepaired pre-mutational UV lesions are repaired in the presence of 5-bromouracil.
(Received June 15 1977)