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Genetics linkage question: is this woman a carrier?
Given: Hemophilia and colorblindness are 10 units away from each other on the X chromosome (i.e. they are sex-linked and, if a chromosome has both of them, there is only a 10% chance that they will be inherited separately).
A colorblind man married a woman who has one 'clean' X and one X that carries both hemophilia and colorblindness. They have a colorblind daughter. What are the chances that
1-she is a carrier of hemophilia and
2-she will pass the disease on to a future son?
This isn't a pure Mendelian question, this is about linkages.
I know that the answer to the first part is that she has a 90% chance of carrying hemophilia. (I did a punnet's square and got 4 possibilities:
1-daughter got the 'clean' X: no hemophilia, no colorblindness
2-daughter got the X with hemophilia and colorblindness
3-daughter got a 'crossover' X: colorblindness, but no hemophilia
4-daughter got a 'crossover' X: hemophilia, but no colorblindness
Options 3 and 4 together have a 10% chance of happening, meaning each one only has a 5% chance (and meaning that the other options have a combined 90% chance of happening, or 45% each).
She could only be option 2 or 3 (because she is colorblind and those are the only ones that result in colorblindness), so she has a 90% chance of option 2 and a 10% chance of option 3.
But I still don't know the chances of passing it on to her son (other than the fact that it is NOT).
50% and my teacher seemed to indicate that it isn't 45% (my first guess) either).
2 Answers
- N ELv 71 decade agoFavorite Answer
I don't see anything wrong with your answer of 45%. She is colorblind and will pass the coloblindness allele to her son. She has a 90% of carrying the hemophilia allele, so the chance that she would pass on the hemophilia allele to her son is the product of the possibilities of passing on the hemophilia allele (50%) and the possibility that she has the hemophilia allele (90%): 1/2 x 9/10 = 9/20 = 45%
- 1 decade ago
well both hemo. and colorblind are on the same chromosome and only 10 units away, so it's most likely they're inherited together.
hc=hemophilia and colorblindness
c=colorblind
I did a punnett square and got the colorblind daughter as XhcXc.She definetly carries hemophilia so i guess it's 100%.
For a son, she can have either XY or XhcY. Since she has a 50% chance of a having a son, that means half of them must have the disease. So 50 divided by 2 is 25. 25% chance of a son having the disease.
I don't know how to draw a punnett box here, but what you do is you put on X and on Xhc on the top. On the sides, you put one Xc and Y
