A S96/YJM789 hybrid strain was sporulated43 (link), and genomic DNA — from 51 wildtype and 5 msh4 tetrads as well as from 20 mms4, 13 S96 parental, and 12 YJM789 parental spores — was extracted from single-colony cultures and hybridized to a custom-designed tiling microarray44 (link). (S96 is isogenic to S288c16 (link),17 (link).) Normalized45 (link) fluorescence intensities corresponding to the set of probes covering each polymorphism were analyzed by applying multivariate semi-supervised clustering to the combined parental and segregant data. Segregant genotypes were assigned using posterior probability of class membership. To reduce genotyping errors, we applied filters to whole arrays, to probe sets and to individual genotype calls. DNA sequencing of ∼60 kb confirmed 100% of filtered genotype calls. After grouping data by tetrad, pairs of genotype change points isolated from all other changes were called NCOs if they involved one spore, or COs if they involved two. Complex groups of genotype changes were annotated as described in Supplementary Figure 3. To calculate event rate along the genome, it was necessary to adjust for varying intermarker interval size. Because individual recombination events typically overlapped multiple intermarker intervals, a novel adjustment procedure was used (Supplementary Information). We defined three types of hot spots — CO, NCO, and overall recombination events — by identifying runs of contiguous intermarker intervals involved in more recombination events than expected under a homogeneous genomic rate. To assess CO/NCO bias, we compared the number and size of intermarker intervals exhibiting more/fewer COs than expected to the corresponding null distribution, generated via simulation. We tested for interference — between consecutive events of the same type and also between COs and NCOs — by comparing the median distance between adjacent, same-tetrad events to medians computed after tetrad label randomization. This randomization strategy preserved hot and cold spot structure but removed interference.