Features of Recent Codon Evolution: A Comparative Polymorphism-Fixation Study

Table 1

Comparison of mutations 𝐺/𝐶→𝐴/𝑇 and 𝐴/𝑇→𝐺/𝐶 at the polymorphic and fixed sites in coding regions.

	Position 1		Position 2		Position 3		Total
	Poly (%)	Fixed (%)	Poly (%)	Fixed (%)	Poly (%)	Fixed (%)	Poly (%)	Fixed (%)
G/C→A/T	1547 (50.9)	1443 (48.7)	1324 (59.2)	1051 (55.4)	3791 (57.5)	4369 (41.7)	6662 (57.6)	6863 (47.8)
A/T→G/C	831 (33.7)	991 (39.3)	793 (26.6)	878 (31.4)	1593 (32.6)	3937 (50.6)	3217 (30.2)	5806 (42.8)
𝑃-value	3.7×10^−5		2.0×10^−7		1.3×10^−95		1.8×10^−90

The frequency of each mutation type was included in the parentheses. 𝑃-values were calculated by χ ² test for 2×2 contingency tables at each position or for the total data. Poly: polymorphisms. Fixed: fixed substitutions.