A woman who is a carrier for hemophilia marries a man who does not have hemophilia. What are the chances of them having a son or daughter with hemophilia? Show your work.
I need help with this short-answer/essay/written problem. I think the answer to this problem is 50% due to the fact that a child inherits EXACTLY 50% of the chromosomes from each of both parents, but I'm not 100% sure. Many thanks to whomever lends me a helping hand with this problem!
"a man who does not have hemophilia." it says very clearly that he is not a carrier.
If only the mother is a carrier, then none of the children will show the trait, but all offspring would have a 50% chance of being a carrier.
Hh x HH
1/2 HH
1/2 Hh
If the father is a carrier, than there is a 50% chance of the children being a carrier and a 25% chance of the children expressing the trait.
Hh x Hh
1/4 HH
1/2 Hh
1/2 hh
The question doesn’t say whether or not the father is a carrier — it just says that he doesn’t express the trait.
Oh wait never mind, I didn't catch the difference between being a carrier and actually expressing the trait/ not expressing it.
Thank you so much for your response, Anonymous! I really appreciate it!
The kid would have a 25% chance of showing the trait. If its asking for carrier too, that would be a different story but for my explanation I will focus on the 25% expressing.
Letters in parenthesis are supposed to be in superscript. The mom is a carrier so her genotype would be:
X(H)X(h)
The dad is not a carrier so he would be:
X(H)Y
Now after putting those genotypes into a punnet square, you will get:
25% X(H)X(H) which is healthy female (non-carrier)
25% X(H)X(h) which is carrier female
25% X(H)Y which is healthy male
25% X(h)Y which is effected male w/disease
Now if the question was asking how much of a chance does the child have of being a carrier OR directly affected, then the answer would be 50% but only showing would be 25%
If only the mother is a carrier, then none of the children will show the trait, but all offspring would have a 50% chance of being a carrier.
Hh x HH
1/2 HH
1/2 Hh
If the father is a carrier, than there is a 50% chance of the children being a carrier and a 25% chance of the children expressing the trait.
Hh x Hh
1/4 HH
1/2 Hh
1/4 hh <== typo correction
The question doesn’t say whether or not the father is a carrier — it just says that he doesn’t express the trait.
To answre this question, we need to know a few facts about hemophilia.
It is an X-linked recessive defect, which means that it is present only on the x-chromosome, and in females, which has 2 x-chromosomes, will require both copies to be defective to have the disorder. If only one x-chromosome is affected, she will be a carrier.
On the other hand, males have only one x-chromosome (the other one is a y-chromosome). Therefore males will either exhibit the disorder, or be just normal. Males cannot be carriers.
For the given problem, the mother is a carrier, and the father does not have the disorder.
Using
X=chromosome with disorder, and
x=normal,
we have the following Punnett square
x y
X Xx Xy
x xx xy
This means that there will be four outcomes, each with probability 25%:
continued:
(where Xx is the carrier mother, xy is the normal father)
Outcomes (each 25%)
Xx = daughter is a carrier
xx = daughter is free from hemophilia
Xy = son had hemophelia
xy = son is free from hemophelia