A question about sex linked traits(colorblindness)

Ok I have a new thought provoking question… My Nephews Father Is color blind. Today He told My sister that if their son is not color blind that it could not be his. I think that is really off…Just because his Dad is colorblind does not mean that he has to be color blind. Or so I think…I tried to work it out with a punnet sqaure But I cannot remember how to do sex linked traits…So who is right? If I am wrong its ok too…but then can someone explain to me how it works?

Colour blindness is hereditary but the condition is passed via a rogue gene from the mother rather than the father.

About 5% of all males are so affected. Women carry the gene but are not subject to colour blindness themselves.

You’re right. Color blindness is carried on the X chromosome. Girls get one X chromosome from each parent. Boys get an X chromosome from their mother and a Y chromosome from their father, so there’s no way a son can inherit colorblindness from his father – his only X chromosome comes fron the mother, so she would have to be a carrier. On the other hand, a girl can only be colorblind if her father is colorblind and her mother is a carrier.

Hope that makes sense.

Unless I’m mistaken, the gene for colorblindness is carried on the X chromosone. Which means that it’s impossible for a father to pass the gene on to a son - the son can only be colorblind if the mother was a recessive carrier of colorblindness. Fathers only pass the Y chromosone onto their sons.

Could be wrong on that, though. It’s been a few years since I learned it in school.

It’s about 8% for males and 1% for females.

There’s various types of “color vision deficiency”, the most common by far is so-called red-green color blindness (and this can be broken down into sub-types)

In my household 100% of the males are color blind!

If it was not so bad a subject it would be funny…We can’t explain to him for anything that His son does not have to be colorblind just because he is…He is convinced that we are nuts:D Thanks for all the info!

Hopefully your nephew’s father’s stupidity isn’t hereditary. :rolleyes:

One more time. The colorblindness gene lives only on the X chromosome. Men only have one of these. If they give their X to their child the child is a girl. If they give their Y to the kid, the kid is a boy.

If you think carefully - there is no way he can pass on his colorblindness to his sons. If they are colorblind they get the trait from mom. His daughters, however, will all be carriers of the trait.

Also - there are colorblind women. I’m one of them. We’re rare, but we do exist.

This factoid will also tell you that my father is also colorblind, and my mother an unaffected carrier. A woman needs a double-whammy to have the condition.

I’m one, too. My optometrist didn’t believe me, until I took one of the colorblindness tests (with the colored dots and numbers). It’s pretty mild–in fact I only notice on those tests. Also–this means any sons I may have MUST be colorblind.

And K364, I’m not trying to do more nitpicking, but my high school bio book said about 1/20 men were colorblind. Doing the population genetics statistics, that worked out to about 1/400 women being colorblind. But then, that was 4 years ago, so maybe I’m not remembering correctly, or maybe (gasp!) the book was wrong.

easy e… I tried to find an authoritive study on the net and didn’t turn up anything, however there were many sites all agreeing with 8%, or 1 in 12. One site said 1 in 10.

I would think it varies by race, gene pool, etc.

Might also vary by how you define “colorblind”. Although the red/green problem is the most widely known, it’s not the only one. Also, not everyone is equally affected. From the description, Easy e and I probably have one of the mild variations that usually go undiagnosed well into adulthood and have a very minimal effect on the person’s life. There is also some evidence that women carriers have slightly affected vision that will not show up on a many color vision tests but will show up on a very sensitive one. In my case, I have passed color vision tests in the past, but not the one given by the FAA which is far more sensitive than the ones I had previously encountered. So some folks might regard my color vision as normal (because I pass one test) but others would not (because I failed a different one).