X-ray-induced specific-locus mutations in the ad-3 region of two-component heterokaryons of neurospora crassa

The induction of specific-locus mutations in the ad-3 region of Neurospora crassa after X-irradiation was studied in a two-component heterokaryon to determine: (1) the ratio of reparable ad-3 mutants to irreparable ad-3 mutants and (2) the induction kinetics of each class. In the present paper, a random sample of 832 X-ray-induced ad-3 mutants of genotype ad-3A or ad-3B that are irreparable have been subjected to more extensive genetic fine-structure analysis. These experiments were designed to determine the extent of the functional inactivation in individual mutants in de ad-3 and immediately adjacent genetic regions in mutants classified as presumptive multilocus deletions or multiple-locus mutations. These experiments have shown that in Neurospora crassa most X-ray-induced irreparable mutants of genotype ad-3A or ad-3B map as a series of overlapping multilocus deletions. Among the 29 irreparable mutants of genotype ad-3A, there are 16 different subgroups of complementation patterns; and among the 63 irreparable mutants of genotype ad-3B, there are also 16 different subgroups E (Author). 24 refs.; 3 figs.; 7 tabs