Non-Mendelian genetics — A/L Biology

How do I practise Non-Mendelian genetics?

1 question with a worked solution

1. A woman with blood group A whose father had blood group O marries a man with blood group B whose mother had blood group O. What is the probability that their first child will have blood group O?
   1. A) 1/8 (12.5%)
   2. B) 1/2 (50%)
   3. C) 0 (0%)
   4. D) 1/4 (25%)
   Check my answer

   Correct answer: D) 1/4 (25%)

   The woman has genotype I^A i (inherited allele i from her O father). The man has genotype I^B i (inherited allele i from his O mother). The Punnett cross (I^A i × I^B i) produces genotypes I^A I^B (AB), I^A i (A), I^B i (B), and ii (O) in equal 1/4 proportions. Probability of group O (ii) is 1/4.

   Show worked solution

   Step 1: Determine genotypes: Woman = I^A i, Man = I^B i. Step 2: Gametes: Woman produces 1/2 I^A and 1/2 i; Man produces 1/2 I^B and 1/2 i. Step 3: Offspring matrix: 1/4 I^A I^B (AB), 1/4 I^A i (A), 1/4 I^B i (B), 1/4 ii (O). Step 4: Probability of ii = 1/4 = 25%. Answer: 1/4 (25%).
   Modelled on: the A/L Biology examination pattern

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Where does Non-Mendelian genetics fit in the syllabus?

Year 1 · Term 2