Abstract
The ad-8 mutants in N. crassa were obtained spontaneously or after treatment ultraviolet, X-rays, nitrous acid, ethylmethanesulfonate, 5-bromodeoxyuridine (BUDR) and/or 5-fluorodeoxyuridine (FUDR). The distribution of mutations on the fine structure map at the ad-8 locus in N. crassa was analyzed. Multiple occurrences of independent mutetions at particular sites (hot spots) were confirmed for mutants of spontaneous origin and ones induced by BUDR and/or FUDR and UV irradiation. Spontaneous and X-ray-induced mutations were characterized by the frequent occurrence of multisite mutations. That the results obtained in a eucaryote, Neurospora are consistent with conclusions from a procaryote, bacterio-phage was emphasized. It was suggested that accumulation of these evidences will elucidate a general statement on the specificity of various types of mutations in all organisms.