Further evidence of a disparity between conversion and restoration in the his1 locus of Saccharomyces cerevisiae

Summary Heteroduplex repair models of recombination predict that restoration of the parental genotype from heteroduplex will have the same frequency as conversion to the genotype of the homologue. We have reported previously (Savage and Hastings 1981) that the proportion of intragenic reciprocal events in the his1 locus of yeast is too low for this expectation. In this study, two classes of recombination event involving longer lengths of his1 are compared in a series of crosses using a constant right-hand marker. This comparison gives a value for conversion: restoration for the left-hand markers which is independant of the method used before. The values obtained by the two methods are significantly correlated, confirming that there is a disparity in the ratio of conversion to restoration, and that this disparity is seen as a deficiency of restoration for five alleles of his1.