Nikesh Lagun , Kushal Budha

Hangzhou International Innovation Institute, Beihang University, Hangzhou, Zhejiang, 311115, China
Author    Correspondence author
Biological Evidence, 2026, Vol. 16, No. 5   
Received: 26 Aug., 2026    Accepted: 14 Sep., 2026    Published: 19 Sep., 2026

This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Human eye colour is a complex pigmentation phenotype in which HERC2 rs12913832 has one of the strongest known single-variant associations, yet a large genetic effect does not imply one-to-one assignment of categorical eye colour. The original Iraqi IrisPlex pilot study evaluated the combined six-SNP prediction system; here, we performed a focused secondary analysis that isolates rs12913832 and directly quantifies its association with the recorded phenotype categories. Participant-level genotype and observed eye-colour data from all 58 Iraqi individuals were analysed as G/G, G/A, and A/A versus blue, intermediate, and brown eye colour in a 3×3 contingency framework. Because expected cell counts were sparse, the primary analysis used a two-sided Fisher–Freeman–Halton exact test, with Cramér's V as the effect-size measure and Pearson's chi-square as a sensitivity analysis. Eye colour comprised 7 blue, 25 intermediate, and 26 brown phenotypes; genotype counts were 18 G/G, 19 G/A, and 21 A/A. Genotype and phenotype were substantially associated (exact p=4.99×10⁻¹⁰; Cramér's V=0.60), with concordant Pearson evidence (χ²(4, N=58) =42.28, p=1.46×10⁻⁸). All blue-eyed participants were G/G, and 19 of 21 A/A participants were brown-eyed, while the heterogeneous intermediate category occurred in every genotype class. These findings provide a transparent population-specific estimate of the rs12913832-eye-colour association in this Iraqi pilot dataset while showing that the recorded three-category phenotype is not uniquely determined by genotype at this single locus.

HERC2; rs12913832; Eye colour; Genotype-phenotype association; Human pigmentation; IrisPlex