Association of polymorphic sites in the OCA2 gene with eye colour using the tree scanning method

A number of genes are considered to affect normal variation in human pigmentation. Recent studies have indicated that OCA2 is the crucial gene involved in the high variation of iris colour present among populations of European descent. In this study, eleven polymorphisms of the OCA2 gene were examined in search of their association with different pigment traits. The evolutionary tree scanning method indicated that the strongest phenotypic eye colour variation is associated with the branch defined by nonsynonymous change rs1800407, which refers to amino acid causing change Arg419Gln located in exon 13. Single SNP analysis indicated that allele 419Gln is associated with green/hazel iris colour (p < 0.001). According to tree scanning analysis, the proportion of eye colour variation explained by this nucleotide position is merely 4%. Thus, additional variation present in the OCA2 gene and perhaps some other pigment related genes must be taken into account in order to explain the high phenotypic variation in iris colour.