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WAEC Biology 2009 Question 56

Question 56

Chromosomes, DNA and Sex Linkage

A man who is heterozygous for the disease haemophilia marries a woman who is double recessive for haemophilia. What percentage of their offspring would have the disease?

  1. A.0%
  2. B.25%
  3. C.50%
  4. D.75%
Show the answer and explanation

Answer: C (50%)

Explanation

Crossing Hh × hh gives Hh and hh in equal numbers, so half (50%) of the offspring are hh and show the disease.