Fig. 4

Kr distributions for palindromic (a) and non-palindromic (b) orthodox R-M system sites. Histograms for the prokaryotic control dataset are shown with dashed red (a) and blue (b) lines, for the actual pairs dataset with dotted orange (a) and green (b) lines. Kr thresholds are marked by vertical lines. The prokaryotic control datasets are the same as in Fig. 2