• Question: Why are our irises different colours?

    Asked by to Naomi on 19 Jun 2014. This question was also asked by .
    • Photo: Naomi Osborne

      Naomi Osborne answered on 19 Jun 2014:

      If the cells in our eyes can produce melanin, we have brown eyes – if we don’t we have blue or green eyes. The ability to produce melanin is controlled by two or more genes inherited from your parents. How these genes interact to make eye colour is still unknown. Babies are all born with blue eyes – if they have genes able to produce melanin, their eyes turn brown at around 1 year old.

      Some people can have two different coloured eyes (although this is rare) – my chemistry teacher had one blue and one brown one. This is thought to be down to varied expression of these genes (and maybe others which we still don’t know about) in the cells of each eye.

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