This is a genetics probability question. In humans, hemophilia A is an X-linked

Question

This is a genetics probability question.

In humans, hemophilia A is an X-linked recessive trait characterized by an abnormality in blood clotting. Albinism is an autosomal recessive trait characterized by the absence of pigment in the skin. A man and woman, both with normal skin pigmentation, have two daughters: one is albino and the other hemophilic. The maternal grandfather had normal blood clotting. The couple plan to have another child. What is the probability that their next child will be:

a.         a son that is normal for both skin pigmentation and blood clotting?

b.         a daughter that is albino and hemophilic?

c.         a child that is a carrier for both traits?

These problems have to be worked out mathmaticly. I dont think it is possible to name all the posible outcomes because some outcomes are more likly than others. this question was already asked on chegg and it was answered incorrectly twice the condition Aa is more likely to occur than AA or aa for part a. and they did not take into consideration that it has to be a boy at first. this problem has many traps. please help

Explanation / Answer

a) is the correct answer,

Here, both parents are with normal skin but not mentioned about hemophilia.

On the basis of the maternal grandfather (normal) and grandmother (hemophilic) genetic background, I assumed that female parent is a carrier of hemophilia (XhX).

But this carrier female would be crossed with a male who is affected by hemophilia (XhY).

It is an X-linked recessive disorder, hence female become a carrier at the heterozygous state (XhX) and male become affected at hemizygous state (XhY). So that we could see one female is hemophilic.

Next, one female is albino, despite the both the parents are normal for the skin. It insists that both the parent would be carriers for albino, since, it is an autosomal recessive disorder.

Here, it is clear that one female is affected so that the other child (female or male) would be normal or carrier for albino. But phenotypically they are considered to be as normal.

In case of hemophilia, the next son would be normal.

XhX x XhY ---- Parents <------------ Grandparents------ XhXh x XY

XhXh XhX XhY XY

Here, we have a chance of a normal son as a next child   

Xx x Xx (albino normal parents in heterozygous state)

XX Xx Xx xx (female is albino as given above)

In that case, the other child would be normal at both the heterozygous (Xx) and homozygous dominant (XX)

So it is clear that the next child would be son and normal for 100%

By joining hemophilia and albino, we can say that the next child would be a son and normal for both hemophilia and skin.   

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