Sliding-window analysis of Ka/Ks for selected pairs of Cenpc genes. Each point represents the value of Ks, Ka, or Ka/Ks for a 99 nucleotide (33 codon) window plotted against the codon position of the midpoint of the window. Ka/Ks is not defined where Ks = 0. The aligned coding sequence is represented at the top of each graph, with the CENPC motif represented by a filled rectangle; exons are also indicated for the plant sequences. Regions of statistically significant positive selection (black bars) and negative selection (gray bars) are marked. (a) Rat and mouse. The interrupted gray bar indicates that p = 0.06 for this region. (b) Arabidopsis thaliana and Arabidopsis arenosa. (c) Maize (CenpcA) and Sorghum bicolor. (d) Wheat and barley, exons 9p-14.