GENETIC STUDIES OF UREASE MUTANTS IN NEUROSPORA CRASSA

Urease-defective mutants, genetic symbol ure, from Neurospora crassa were studied genetically with the use of known markers in crosses. A method was developed for rapid testing of urease activity in cultures from ascospore isolations. Two ure mutants, isolation numbers (9) and (47), respectively, were located in the right arm of linkage group V, approximately 30 crossover units from the centromere. The two ure mutants are at separate loci at a distance of approximately 3 c.o. units. They are separated by the gene am. Recombination between the two ure loci was studied using the closely linked markers am1 (32213) and hist-1 (C91). A screening procedure was used to select for rare recombinant types from among random ascospores. A 1 ure+:ure- segregation of spore pairs within dissected asci was found in crosses between ure mutants (9) and (47). Mutants from the two ure loci complements to form urease-positive heterokaryons. The urease mutants are designated with a locus and an allele (isolation) numbers as ure-1 (9) and ure-2 (47), respectively, for future use. The results are discussed in relation to other complex gene-enzyme systems in Neurospora. © 1966.