Why are your eyes that colour?

THAT'S THE WHY:Jeepers creepers, where'd you get those peepers? Well to a large extent you inherit your eye colour, but why did you get your own particular hue?

If you studied biology in the past you may have come across the teaching of eye colour being a dominant (brown) or recessive (blue) inherited trait, but in recent years studies have pointed to a more complicated genetic picture.

The pigments in the iris lend your eyes those brown, blue, hazel, green or gun-metal grey tones, and many genes involved in pigment production are thought to be involved.

One gene that appears central to the process is OCA2. Research suggests that variations that affect this gene have the lion’s share of influence on eye colour.

A Danish study found that variation in a specific portion of the HERC2 gene tones down OCA2 in a manner that’s linked with blue eyes – and they speculated about its origin.

"The mutations responsible for the blue eye colour most likely originate from the near east area or northwest part of the Black Sea region, where the great agriculture migration to the northern part of Europe took place in the Neolithic periods about 6,000-10,000 years ago," wrote the authors in Human Geneticsin 2008.

More recently, papers in the Journal of Human Geneticshave been thrashing out the issues further. One last month describes how gene-gene interactions may conjure up the palettes of hazels and greens, while a review paper in January points to complexity in how the genes are expressed: "With all genetic expression, aberration also occurs. Some individuals may express two phenotypes – one in each eye – or a complete lack of pigmentation, ocular albinism."