Figure 1.

Schematic representation of chromosome 6, the MHC region, location of HLA loci and variation within a specific locus (HLA-B). Top: Chromosome 6, showing approximately 4 Mb region comprising the MHC, within which HLA genes are located. Middle: MHC region, with classical HLA class I and HLA class II loci. Bottom: Representation of six sequences of the HLA-B coding region, with SNPs represented as circles, with the colour indicating the allele at that position. Analyses of diversity can be carried out over SNPs (with one SNP represented by the vertical rectangle) or over HLA alleles (in this figure, there are five distinct HLA-B alleles which are named, among the six chromosomes sampled).