Variation of amino acid residues in exon 2 of the MHC I gene encoding for the α1 chain of the MHC molecule. Residues of the 27 alleles detected are given following the reading frame in . The variation for each residue is based on the number and frequency of substitutions and is calculated as y = 1-Valdar01 score, as determined with the Scorecons server by . Grey bars represent sites predicted to be under positive selection, * denotes predicted conserved peptide-binding residues of antigen N and C termini, + denotes predicted salt bridge-forming residues. Primer positions have been removed.