The HLA-DRB1 exon diversity. A, DRB1 exon 2 diversity compared to the rest of the coding region (fused exons 1, 3, 4, 5 and 6) in the dataset including the entire DRB1 coding region (49 sequences). Mean ± sem is shown. B, synonymous and non-synonymous diversity in the DRB1 coding region in the dataset including the entire DRB1 coding region. In the short exon 5 (24 bp) half of the alleles have G instead of C at the nucleotide position 22, resulting in high apparent diversity for the whole exon. Mean ± sem is shown. C, sliding window analysis of non-synonymous, synonymous and complex substitutions in the DRB1-e2 in the dataset including the complete DRB1-e2. Complex stands for complex combinations of non-synonymous and synonymous substitutions in the same codon. The graph illustrates the contribution of these different components in d, which is not equal to d
(d, as calculated here does not take into consideration the capability of the codon to mutate in synonymous and non-synonymous manner).