Recombination Mechanisms at the pan-2 Locus in Neurospora crassa

Abstract

The nature of the mechanisms responsible for recombination between closely linked, functionally similar mutants has become of increasing significance in recent genetic investigations. Much evidence now indicates that crosses between such mutants may exhibit behavior unexpected on the classical theory of recombination, which involves reciprocal crossing over at the four strand stage of meiosis accompanied by positive chromosome interference. This evidence, which is now available in a variety of microorganisms, came initially from the observation that prototrophs recovered in random ascospore platings from crosses of apparently allelic auxotrophic mutants having closely linked markers on either side of the locus under investigation, occur in all four categories with respect to the markers—the two parental and the two crossover (Giles, 1951, 1956; Pritchard, 1955; Calef, 1957).