Complementation between Alleles in Heterocaryons

Abstract

Two cases have been described recently in Neurospora crassa in which mutants, each lacking a particular function, show partial manifestation of the function when combined in a heterocaryon. These cases concern, respectively, mutants affecting glutamic dehydrogenase (Fincham and Pateman, 1957) and adenylosuccinase (Giles, Partridge and Nelson, 1957). For each, there is a number of mutants, every one of which completely lacks the specific function. Each set of mutants is divisible into three groups, A, B and C, on the basis of heterocaryon complementation. Primarily this is detected by the ability of heterocaryons to grow on minimal medium, in the absence of a supplement of the growth factor specifically required by the mutants. Group A shows no complementation with either group B or group C, but B and C complement one another. Of course, there is no complementation between members of the same group.