The eyes have it

The eyes have it - Scientists have uncovered a clutch of new genes linked to eye colour.

Previously seven genes have been implicated in human eye colour, but the categorisation of eyes as blue, brown or green is widely recognised as a gross over-simplification.

To shed some light on the problem, Dutch researcher Manfred Kayser from Erasmus University compared the eye colours - as captured by a digital camera - of almost 6000 Dutch people, 2261 UK twins and 1282 Australians, with their DNA.

Using a technique called genome wide association, which involves looking for genetic hotspots that crop up repeatedly in people who carry a certain trait but not amongst people lacking that trait, it was possible to tie up certain genetic regions with certain eye colours.

In all the study, which is published this week in PLoS Genetics, flushed out 3 entirely new genes linked to eye colour and enabled Kayser and his colleagues to build a "model" that can predict over 50% of eye colour variations in the populations they studied. One immediate beneficiary will be forensic investigations, points out Kayser, because it will now be possible to predict, with much greater accuracy, a perpetrator's - or a victim's - appearance.