A dose-rate effect in UV mutagenesis in neurospora.

A simple system for screening a large number of genes for recessive lethal mutations has been used to study dose-rate effects on UV-induced mutation. Acute UV produced 4 times as many mutations as did the same dose given at chronic rate. Chronic UV at 0 degree gave as many mutations as acute UV; this indicates that the prevention of mutation during chronic treatment at 22 degrees results from metabolic repair activities. In a strain which lacked excision repair, acute UV produced twice as many mutations as chronic; this suggests that the dose-rate effect seen in repair-proficient Neurospora results from the action of the excision-repair system as well as from some other repair system.