Selection pressure on cancer/testis (CT) antigen genes between human-chimpanzee orthologs.

<p>(A), Comparison of Ka/Ks ratios between testis-restricted and testis-selective CT genes. To increase the data entry points, the Ka/Ks ratio is given an arbitrary constant of 3 for Ka/Ks = ∞ which has a Ks = 0. The mean or median of Ka/Ks is significantly higher in the testis-restricted group (<i>P</i> = 0.0001 in Mann-Whitney test) than the testis-selected group. (B), Comparison of Ka/Ks ratios for testis-selective genes located on the X chromosome and on autosomes shows no difference (<i>P</i> = 0.69 by Mann-Whitney test).