Table 4. Direction of synonymous codon change in the S288c and YJM789 branches.

	Preferred to unpreferred*		Unpreferred to preferred†
	500 genes with the strongest codon usage bias	Rest of the genes	500 genes with the strongest codon usage bias	Rest of the genes
S288c	236	1,908	160	1,767
YJM789	203	1,951	153	1,682
S288c/YJM789	1.16	0.98	1.05	1.05

^*Codon preference for each amino acid was taken from ref. 19. χ² test, P = 0.086.

^†χ² test, P = 0.97.