Fig. 4

Purifying selection on the synonymous SNPs in cancer-related genes. a Codon bias (codon preference) of the 59 sense codons in human genome. Codons with a positive value are preferred, and vice versa. b Correlation between codon bias and codon frequency appearing in human genome. c Correlation between the delta codon bias after the synonymous change and the fraction of cancer-related genes. Genes were divided into ten bins with increasing delta codon bias. d Correlation between the delta codon frequency after the synonymous change and the fraction of cancer-related genes. Genes were divided into ten bins with increasing delta codon frequency. “onco” denotes cancer-related genes; “non-onco” denotes other genes