Fig. 2

The relaxation of negative selection on majority of tumor somatic mtDNA single base mutations. a, b, c, d Proportion of synonymous and nonsynonymous single base mutations in mRNA-coding regions, benign and deleterious in tRNA coding regions, mutations with different damage grades in mRNA coding regions, those resulting in different codon substitutions in population, tumor and simulation data (Left); Proportion only in tumor data stratified by heteroplasmic levels (Middle); Average heteroplasmic level in tumor data (Right). CC: codons completely complementary to anti-codons. NCC: codons not completely complementary to anti-codons. Left and middle: chi-square test was used. Right (a, b): t test was used; Right (c, d): ANOVA was used