Genetic factors influencing crossing-over frequency in Neurospora.

D I F F E R E N T crosses involving the same marked region in Neurospora crassa may yield markedly different frequencies of recombinants. It has been suggested that the fluctuations in recombination frequency result from inherent differences between the various wild-type strains from which the stocks descended (BARRATT 1954; FROST 1961). However, the nature of these differences and the ways in which they may influence the crossing-over process remain unknown. The present report deals with experiments designed to pursue the following questions about genetic factors which influence the frequency of crossing-over: ( 1 ) Are factors at a single genetic locus responsible for these effects? (2) Is the frequency of crossing-over influenced by the presence of particular