Abstract
The distribution of mutations on the fine structure map at the ad-8 locus in Neurospora crassa has been analysed. Multiple occurrences of independent mutations at particular sites (hot spots) have been confirmed for mutants of spontaneous origin and ones induced by bromodeoxyuridine and/or fluorodeoxyuridine and by ultraviolet irradiation. Spontaneous and X-ray-induced mutations were characterized by the frequent occurrence of multisite mutations. Discussions have been made on the possible mechanisms of mutations in comparison with some conclusions obtained in bacteriophage T4.
