Density of recombinations for all autosomes compared to a Poisson model. We scored the number of recombinations for each of 2,072 chromosomes (all strains; chromosome X excluded). The mean number is 2.43 recombination breakpoints per chromosome. The particular distribution assumes all 19 autosomes have a length of about 70 cM and this simplification accounts for the high Χ2 (125, p << 0.001, 10 df). Of 250 non-recombinant chromosomes observed only 182 were expected. There are also significantly more chromosomes with an apparent excess of recombinations. These deviations are of course expected because short chromosomes (<70 cM) will contribute more non-recombinants and long chromosomes (> 70 cM) will contribute more highly recombinant chromosomes than predicted by the model.