Fig. 1

C > T polymorphism rate in the human population and classification of CpG islands (CGIs). a Schematic illustration of the classification of CGIs. b The distribution of the size of the CGIs according to the CGI types. CGIs related to a transcriptional start site (TSS) are significantly longer compared to the others. c The statistics of CpG dinucleotides in the reference human genome. Among C or G at the CpG dinucleotide sequence context, approximately 7% are located in CGIs. Approximately half of the CpGs in CGIs are located in the TSS-coding CGIs. d Mutational spectrum accumulated during human genome evolution. Decomposition of the mutational spectrum revealed that C > T transitions at the CpG contexts (Signature 1) were one of three major signatures during human genome evolution. e Mutation rate of CpGs based on CGI classifications (Error bars indicate 95% confidence intervals). Interestingly, intragenic coding CGIs have the highest mutation rate among the five CGI types. f The distribution of allele frequencies of the C > T transitions according to the CGI types. As the higher the mutation rate of the CpGs in e becomes higher, the absolute value of allele frequencies tends to be higher. A logarithmic scale is applied to the y-axis