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JAMB Biology 1995 Question 45

Question 45

Chromosomes, DNA and Sex Linkage

All the sons of a colour-blind woman will be colour blind regardless of the state of the father because

  1. A.the egg determines the phenotype of the son
  2. B.sons inherit the sex chromosomes of their mothers
  3. C.the father's sex chromosome is weaker in sons
  4. D.sex-linked traits express dominance in females.
Show the answer and explanation

Answer: B (sons inherit the sex chromosomes of their mothers)

Explanation

A son receives his X chromosome from his mother and his Y from his father. A colour-blind mother has the gene on both X chromosomes, so every son gets it.