Marey maps showing genetic distance plotted against physical position. The general tendency is close to a straight line. Chromosome 4 is the best example of this linearity. Chromosome 1 shows that the centromeric region does not affect the linear relation (see text for discussion). Chromosomes 10 and 16 show the greatest irregularities. Gaps between scaffolds have been ignored (that is, set at 0 kb) but the graphs obtained fixing the gaps to 50 kb are indistinguishable from these ones.