Cited research: PLoS Genet. 6, e1000934 (2010)

Previous studies of the genetics of human eye colour used only broad categories — such as blue, brown and intermediate — without quantifying the subtle variations in between. So far, this has led to the identification of seven genes associated with the trait.

Manfred Kayser at Erasmus University Medical Center in Rotterdam, the Netherlands, and his colleagues adopted a more detailed approach. They digitally encoded eye colour using hue and saturation values obtained from high-resolution photographs of 5,951 Dutch Europeans.

Analysis of the participants' genomes revealed three new regions associated with continuous variations in eye colour. These new regions, together with the seven genes identified previously, underlie about 50% of eye-colour variation, according to a model the researchers developed to predict eye colour. J.F.