THE MUTATION SK(ad-3A) CANCELS THE DOMINANCE OF ad-3A+ OVER ad-3A IN THE ASCUS OF NEUROSPORA

[摘要] A newly induced mutant of Neurospora, when crossed with an ad-3A mutant, produces asci with four viable black and four inviable white ascospores. The survivors always contain the new mutant allele, never ad-3A . The new allele, which is called SK(ad-3A) (for spore killer of ad-3A ), is located at or very near the ad-3A locus. —In crosses homozygous for ad-3A , each ascus contains only inviable white ascospores. This defect in ascospore maturation is complemented by the wild-type allele, ad-3A + (crosses heterozygous for ad-3A and ad-3A + produce mainly viable ascospores), but it is not complemented by the new SK(ad-3A) allele (all ad-3A ascospores from crosses heterozygous for SK(ad-3A) and ad-3A are white and inviable). In crosses homozygous for SK(ad-3A) or heterozygous for SK(ad-3A) and ad-3A +, each ascus contains only viable black ascospores. SK(ad-3A) does not require adenine for growth, and forced heterokaryons between SK(ad-3A) and ad-3A grow at wild-type rates and produce conidia of both genotypes with approximately equal frequency. Thus, the action of SK(ad-3A) is apparently restricted to ascospore formation. Possible mechanisms of the action of this new allele are discussed.

[学科分类] 医学（综合）