Wow

[Tiarali]

(07-04-2012 10:47 PM)Don Wrote:  

(07-04-2012 10:35 PM)dramaturge Wrote:  I'm bothered by the fact that the article says this apparently happens on a regular basis. That seems like a huge cop-out: "Oops, I pushed the wrong button; I'd like to change my vote." I wonder how often that really means, "I voted X because I thought that was right, but I need to change it to Y now so my voting record looks good." I mean, seriously: even if you're red-green color blind, not only are the words on the buttons, like Historian said, "Aye" is the top button and "No" is the bottom one. Pretty sure that doesn't change between votes or desks....

I didn't think females could be colorblind? I thought that was a male genetic trait.

Colourblindness is recessive and carried on the X chromosome. So if a guy gets an affected X chromosome, then the pairing chromosome will be Y so there won't be a corresponding dominant trait (non-colourblindness) to overrule it, so any male who receives the colourblindness trait from his mother (his father gives the Y chromosome) will be colourblind.

A girl, however, gets two X chromosomes - one from her mother and one from her father. If she gets an affected X chromosome from either parent, she will still exhibit the dominant (non-colourblindness) trait that is present in the other chromosome.

If the girl, however, gets two colourblind X chromosomes, so BOTH parents have an affected chromosome (meaning the father would be colourblind and the mother might be colourblind or might just be a carrier) then she will actually be colourblind herself. This is, of course, very rare.

Either way, the girl who gets only one affected X chromosome is automatically a carrier - in each of her children, she will have a 50% chance of giving them the affected chromosome. So 50% of her daughters are likely to be a carrier of colourblindness without being colourblind themselves, and 50% of her sons are likely to be colourblind. Unless, of course, she marries a colourblind man, in which case all of her daughters will be carriers, and 50% of them might also be colourblind.

Also, if a colourblind man has only sons, then since he will not have passed on the affected X chromosome at all, then the colourblindness trait will have died out in his particular branch of the family.

Source: My husband is colourblind, and my daughters are therefore all carriers of it. Interestingly enough, all the boys (4) in his family are colourblind, even though statistically speaking they only had a 50% chance.

Edit: I wasn't aware that you could also develop colourblindness. I did know there are several different types, just wasn't aware that they were obtained differently.