Punnett square help, I'm lost?

Question

Red-green colorblindness is a sex-linked trait. A woman with normal color vision, whose father was colorblind, mates with a colorblind man. What chance do each of their sons have of being colorblind?

Answer 1

50% chance. A Punnett Square is kinda hard to do up here, so let me just try and explain it.

Females have 2 X chromosomes and therefore 99% of the time do not have suffer from sex-linked conditions. They have 1 x chromosome coming from each of their parents.

Males, however, only have 1 X chromosome, coming from the mother. So already, we can dismiss the traits of the father, since for a male child to be conceived, the father must contribute a Y chromosome, which doesn't determine this trait. If the mother has normal vision, but is a carrier of the color-blindness trait, then a male child will have a 50% chance of receiving that chromosome and trait.

Answer 2

Red-green colorblindness is a sex-linked trait carried on the X chromosome. Since males only have one X chromosome, they only need one copy to exhibit this phenotype. Females need two matched copies to get this trait.

Since the father of the cross is colorblind, he will always contribute a X chromosome with the red-green color blind allele on it, however since he is male his X is only given to his female offspring.

Since the mother's father was colorblind, she would be a carrier for the trait, i.e. at least one of her two X chromosomes would bear the allele for sure. Both of her X chromosomes would not since she did not have this colorblindness.

So this couplings male offspring would have a 50% chance of getting the allele, as one of the mother's two X chromosomes would be randomly selected. The female offspring would all receive the colorblind X from their father and then would also have a 50% chance of getting the colorblind X from their mother. However since females need both to show this characteristic, they too would have a 50% chance of being red-green colorblind.

I know this is more then you were asking, but I hope it explains a lot for you. Hope this helps. :)

Answer 3

all of them will be. it is a genetic trait that follows all of the sons of a girl that has been fathered by a colorblind male. yet none of the daughters. all colorblind subjects are male... always. but none of her daughters sons will be. it is only out of the daughters F1 male generation.

Answer 4

As red green colorblindness is a recessive ale, this means that the woman's is Xx(the small x is for the colourblind) or XX. That color blind man would be xY.

Thus, their son who would have a percentage of 50% of color blind if their mother is Xx and a percentage of 0% if their mother is XX.

I hope this helps. :)

Answer 5

Women- Cc
Man-cc
that would be C c
c Cc cc
c Cc cc

50% chance he will be color blind

Answer 6

WOW i just did that same exact thing for a bio project a couple weeks ago!