Hemophilia is a recessive X-linked trait in humans. If a heterozygous woman has children with a normal man, what are the odds of the following combinations of children?
P. An unaffected daughter or son
Q. Two out of five offsprings that are affected
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P - 1/4 and Q - 52.6%
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P - 3/4 and Q - 26.3%
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P - 3/4 and Q - 50%
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P - 81/256 and Q - 26.3%
B
Correct answer
Explanation
For a heterozygous female (X^H X^h) crossed with a normal male (X^H Y): each child has 1/4 chance of being unaffected (X^H X^H female or X^H Y male). So P (unaffected) = 3/4. For 5 offspring, the probability exactly 2 are affected is calculated using binomial distribution: C(5,2) × (1/4)^2 × (3/4)^3 = 10 × 1/16 × 27/64 ≈ 26.3%.