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JAMB Biology 1994 Question 43

Question 43

Mendelian Inheritance

In the gene locus for eye colour in humans, the allele for brown eyes is dominant over the allele for blue eyes. If a homozygous brown-eyed girl has a brother with blue eyes, what are the likely phenotypes of their parents' eye colour? (Eye colour is not a sex-linked trait)

  1. A.Both parents have blue eyes
  2. B.Their father has blue eyes and their mother has brown eyes
  3. C.Both parents have brown eyes
  4. D.Their mother has blue eyes and their father has brown eyes.
Show the answer and explanation

Answer: C (Both parents have brown eyes)

Explanation

The girl (BB) got a B from each parent and the blue-eyed boy (bb) got a b from each, so both parents are Bb and have brown eyes.