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JAMB Biology 1997 Question 44

Question 44

Mendelian Inheritance

The homozygous condition HbSHbS results in sickle cell anaemia whereas HbA HbS has the sickling trait. What is the probability that a couple with the sickling trait will give birth to one normal child?

  1. A.1/2
  2. B.1/4
  3. C.1/8
  4. D.0.
Show the answer and explanation

Answer: B (1/4)

Explanation

HbAHbS × HbAHbS gives AA : AS : SS in the ratio 1 : 2 : 1, so the chance of a normal (AA) child is 1/4.