[Campbell Biology P.341] Hemochromatosis is a recessive inherited disease. A husband and wif... | Practice Question

Hemochromatosis is a recessive inherited disease. A husband and wife are both carriers. If they have three children, what is the probability that one or more of the children will have the disease?

  • A: 27/64
  • B: 1/64
  • C: 3/4
  • D: 37/64

Explanation

This is a complementary probability problem. First, calculate the probability of the opposite event: that ALL three children are of normal phenotype. For each child, the probability of being normal is 3/4. So, the probability of all three being normal is 3/4 3/4 3/4 = 27/64. The probability of at least one child having the disease is 1 minus the probability that none have it. So, P at least one affected = 1 - P all normal = 1 - 27/64 = 37/64.