Hemophilia is a X-linked recessive disorder affecting individual\'s blood clotti

Question

Hemophilia is a X-linked recessive disorder affecting individual's blood clotting ability. A man (1 ir the pedigree below) whose maternal grandfather has hemophilia married a woman (2 in the pedigree) whose brother has hemophilia (the husband's and wife's parents are phenotypically normal). The couples are expecting their first child. What is the probability that their first child has hemophilia? (Answer in decimal) Individuals with hemophilia are indicated by solid square or circle 2 Submit Answer Tries 0/3

Explanation / Answer

Answer:

Since the man (individual 1) is normal, his genotype is X+, and the woman (individual 2) is also phenotypically normal, indicating that she has at least one X+.

However, as her brother has hemophilia, her mother is likely a carrier, therefore the probability of individual 2 being a carrier is 1/2. Because a daughter will inherit the X+ from the dad (individual 1), only a son (1/2) will be affected and the probability of a son inheriting the Xh from the carrier mom is (1/2). Therefore the probability is:

1/2 x 1/2 x 1/2 = 1/8 = 0.125

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