High frequency of reversion of a nicotinic acid gene in Coprinus radiatus

Summary The cross of the nicotinic acid requiring mutant nic-2 with the wild type strain gives rise to the following tetrads: (2nic ⁺ 2nic ^–), (3nic ⁺, 1nic ^–) and (4nic ⁺). Genetic analysis has ruled out the hypothesis that the nicotinic acid requirement of this mutant is controlled by several loci. The nic-2 marker has been presisely located on chromosome II of Coprinus. It reverts with high frequency (20 to 30%) to the wild type allele. Reversion is not the result of recombination (at least directly). It seems to be an autonomous property of the marker.