Different evolutionary patterns between young duplicate genes in the human genome

Table 1 Substitution rates versus K_a/K_s ratios in duplicate genes

	Different amino-acid substitution rates*	Equal amino-acid substitution rate^†	Total
Different K_a/K_s ratios^‡	54	11	65
Equal K_a/K_s ratio^§	91	94	185
Total	145	105	250

A 2 × 2 chi-square test. χ² = 12.78, df = 1, p < 0.001. The null hypothesis is that the number of pairs with different K_a/K_s ratios is independent of the number of pairs with different amino-acid substitution rates. The values are the observed number of pairs for each category; for example, there are 54 pairs with both different K_a/K_s ratios and different amino-acid substitution rates. The amino-acid substitution rates (or the K_a/K_s ratios) in the two duplicate genes are considered different only if the difference is statistically significant. *Gene pairs with different amino-acid substitution rates between the two duplicates. ^†Gene pairs with equal amino-acid substitution rates between the two duplicates. ^‡Gene pairs with different K_a/K_s ratios between the two duplicates. ^§Gene pairs with equal K_a/K_s ratios between the two duplicates.

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