INDUCED REPAIR OF GENETIC DAMAGE IN NEUROSPORA

Repair of genetic damage in Neurospora has been studied using a procedure in which one strain is exposed to a potentially lethal dose of UV before being joined in a heterokaryon with an undamaged strain. We have monitored the ability of the second strain to rescue the first. The extent of rescue is greatly enhanced when the rescuing strain has itself received a small, nonlethal dose of UV, thus demonstrating an inducible repair system.—The experiment was modified by substituting X rays or nitrous acid for UV as either the damaging agent or the inducing agent. In every combination, induced rescue was observed.——Three repair-deficient mutants (uvs-2, uvs-3 and uvs-6) were substituted for wild type (uvs  +) as the rescuing component to find out whether any of them lacked the inducible repair system. Both uvs-2 and uvs-6 demonstrated inducible repair; uvs-3 showed none, but gave a high level of repair without induction, suggesting that it is a regulation (derepressed) mutant of an inducible repair system.