(A) Gender differences in recombination on human chromosome 21q. A normalized statistic quantifying the difference (ϕ) in recombination rates between female and male meioses (Y-axis) is plotted against the midpoint of each interval across the sex-averaged genetic map (X-axis). One standard deviation unit on either side of ϕ is also plotted. The tick marks at the top of the figure represent the location of the markers on the sex-averaged linkage map. (B) Recombination vs. physical distance on human chromosome 21q. Estimates of kb/cM (Y-axis) are plotted against the midpoint of each interval across the sequence map (X-axis); female and male values are represented by solid and dashed lines, respectively. The tick marks at the top of the figure represent the physical location of the markers used.