Colour Blind

[krugs]

Why are only men afflicted with colour blindness?

[Piljim]

From what I remember, its because the colour blindness gene is attached to the Y chromosome, which females do not have. (Males have XY, females have XX)

[woolley]

It is genetic, but women can be carriers of the defect and pass it on to their children. In this country, about 8% males and less than 1% femals have the problem.

[Ginbottle]

My grandfather was red/green colour blind. I'm male & not colour blind but my mum can't see brown/green, - well mushroom's in a field. & Mum is supposed to be a carrier.

[Herodotus]

Piljim has it backwards - the tendency for colour blindness is caused by the absence of a gene. The normal gene is acrried by the X chromosome, so men only need to inherit one duff gene to be affected. women will get it too, but only if they get two duff genes. A woman with only one faulty gene is a carrier and has a 50% chance of her sons being affected.