4.1 A double heterozygote has the repulsion configuration A b / a B of two linked genes that have a frequency of recombination of 0.20 . If a randomly chosen gamete carries A , what is the probability that it also carries B ? 4.7 Construct a genetic map of a chromosome from the following recombination frequencies between individual pairs of genes: r c , 10 ; c p , 12 ; p r , 3 ; s c , 16 ; s r , 8 . You will discover that the distances are not strictly additive. Why aren't they? .