The rad59 mutant alleles have distinct effects on gene conversion between un-linked repetitive elements in haploid strains. (A) The spontaneous ectopic gene conversion system: Haploid strains containing a sam1-∆Bgl II-HOcs allele at the SAM1 locus on chromosome XII, a sam1-∆Sal I allele at the HIS3 locus on chromosome XV, and the sam2::HIS3 allele at the SAM2 locus on chromosome IV (not pictured) were grown to saturation in YPD supplemented with AdoMet, and plated onto medium lacking AdoMet to select for cells in which a recombination event generates a functional SAM1 gene and an AdoMet prototrophic cell. The opposite orientations of the sam1 alleles relative to their centromeres prevents the isolation of single crossovers. Only conversions of the sam1-∆Bgl II-HOcs allele to wild-type are observed due to the absence of a promoter for the sam1-∆Sal I allele. The sam2::HIS3 allele is missing sufficient information to recombine with sam1-∆Bgl II-HOcs. Black bars indicate the positions of the mutations. (B) Rates of ectopic gene conversion in wild-type and single mutant strains. Rates were determined from a minimum of 10 independent cultures as described in the Methods. Fold decreases (−) and increases (+) from wild-type are indicated in boxes. (C) Rates of ectopic gene conversion in rad27 rad59 double mutant strains. (D) Rates of ectopic gene conversion in rad51::LEU2 and srs2::TRP1 single mutant, and rad51::LEU2 rad59-Y92A and srs2::TRP1 rad59-Y92A double mutant strains.