Characterization of human crossover interference

We present an analysis of crossover interference over the entire human geno me, on the basis of genotype data from more than 8,000 polymorphisms in eig ht CEPH families. Overwhelming evidence was found for strong positive cross over interference, with average strength lying between the levels of interf erence implied by the Kosambi and Carter-Falconer map functions. Five mathe matical models of interference were evaluated: the gamma model and four ver sions of the count-location model. The gamma model fit the data far better than did any of the other four models. Analysis of intercrossover distances was greatly superior to the analysis of crossover counts, in both demonstr ating interference and distinguishing between the five models. In contrast to earlier suggestions, interference was found to continue uninterrupted ac ross the centromeres. No convincing differences in the levels of interferen ce were found between the sexes or among chromosomes; however, we did detec t possible individual variation in interference among the eight mothers. Fi nally, we present an equation that provides the probability of the occurren ce of a double crossover between two nonrecombinant, informative polymorphi sms.