Variation in "Map Distance" in Neurospora crassa

Abstract

Determinations of the same map distance in different crosses often give divergent results, whereas values for unrelated map regions are often strikingly similar. This situation has been examined in samples of serially isolated spore octets, mainly from two-marker crosses. Observed ratios of phenotype distribution classes suggest more systematic modifications of random distributions than would be expected from reassociations, through crossing-over, of chromosome segments chosen unsystematically. Detailed interpretation appears impracticable, since complexities in the general behavior of the organism indicate that the ratios observed may reflect opportunities, occurring at different stages of the life cycle, for successive reassociations of genetic units.