Figure 3.

Phylogenetic tree of human MHC (HLA) class I genes and alleles. The phylogenetic trees presented in this paper are neighbor-joining trees obtained by the computer software mega (35). The tree in this figure was constructed by using Jukes–Cantor distances for the nucleotide sequences (822 bp) of exons 2, 3, and 4, which encode class I MHC domains α₁, α₂, and α₃, respectively. Genes E, F, and G, designated by (b), are functional class Ib loci, whereas genes H, J, 92, and 70, designated by (ψ), are class Ib pseudogenes. Class Ib genes MICA and HH were not included because they are distantly related (see Fig. 4). Two mouse class Ia genes were used as outgroups. The numbers for interior branches refer to the bootstrap values for 500 replications. The bootstrap values less than 50% are not given. The scale at the bottom is in units of nucleotide substitutions per site.