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Abstract
The exposure of tryptophan-requiring Escherichia coli b/r wp2 to u.v.- and γ-irradiation (in either order) results in more revertants than would be expected if the two treatments were independent. The excess mutants (‘interaction mutants’) were produced in increasing number by increasing doses of u. v.-or γ-radiation. Evidence is presented that the interaction occurs post-irradiation. Although the excision-repair and mutation frequency decline systems for u.v. damage are not involved in the interaction itself (since a strain deficient in these systems, E. coli wp2 her–, is no less efficient at producing interaction mutants than E. coli b/r wp 2) the u.v. component involved in interaction is sensitive to one or both of these systems as is shown by the very much lower u.v. doses at which interaction occurs in E. coli wp2 her–.
- Accepted:
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