• Question: How are some people colour blind and others arent

    Asked by Emma The Penguin Lover to Áine, Ciarán, Eoin, Lydia, Victoria on 14 Nov 2014.
    • Photo: Lydia Bach

      Lydia Bach answered on 14 Nov 2014:

      Hey Emma,

      most people who are colour blind have a fault the sensory cells that receive light. Colour blindness is much more common in men than in women – around 8% of all men in the world are colour blind, and only 1% of women!

      That’s because the fault in the sensory cells is caused by genes (the parts of DNA that carry information that make traits of people) that are found on the X chromosome (that’s a structure our genes sit on, we have 46 of them).

      Women have two X chromosomes, but men only have one. So even if a women has one of the broken genes sitting on one X chromosome, she still has the second one which makes up for it and can make working sensory cells. Guys on the other hand only have one X chromosome, so if the genes sitting on it are faulty, they will be colour blind.

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