Fig. 5

Suppressed recombination near K. phaffii centromeres. a Locations of crossovers in the ARG4–HIS4 interval on chromosome 1. A crossover in this interval is obligatory in each of the 11 asci. Two asci (Tetrad 20 and Trio 22) had a second crossover in the interval, making 13 crossovers in total. The centromere (CEN1) is drawn to scale as a gray bar. The low diversity region around CEN1 is indicated by a dashed line. b Distribution of distances from the centromere, for all 269 non-obligatory crossovers in our dataset. The graph shows the cumulative number of crossovers, plotted as a function of their distance from the centromere of the chromosome on which they occur. Data from all four chromosomes was pooled. The cartoon at the top shows the four chromosomes, folded at their centromeres, to show how many chromosome arms exist at any particular distance and hence are available for recombination (two of the eight chromosome arms are very short). Individual plots for each chromosome are shown in Additional file 1: Fig. S3. Obligatory crossovers in the ARG4–HIS4 interval were excluded from the analysis in b. For Tetrad 20 and Trio 22, we arbitrarily designated the more centromere-proximal crossover as non-obligatory and the more distal one as obligatory