Alkylation induced gene conversion in yeast: Use in fine structure mapping

Summary Methyl-methanesulfonate (MMS) causes gene conversions in heteroallelic diploids of Saccharomyces cerevisiae. The frequency of production of prototrophic convertants is linearly proportional to the square of the time of MMS treatment, and the regression of prototrophs on dose varies depending upon the particular pair of alleles present in the diploid. The regressions show an additivity relationship, in that when a triad of heteroallelic diploids of the type m₁/m₂, m₂/m₃, and m₁/m₃ is considered, two of the regressions add up approximately to the third. MMS can, therefore, be used in fine structure mitotic mapping of genes. Good agreement was found both in relative order and spacing of alleles at the histidine 1 locus of yeast when the fine structure map based on the X-ray mapping method was compared with that based on MMS.