O Levels Biology (5090)•5090/11/M/J/22

Explanation
Pedigree-based genotype probability for individual 10
Steps:
- Identify the genotypes of individual 10's parents from the pedigree: one homozygous dominant (AA) and one heterozygous (Aa).
- Determine possible genotypes for individual 10: AA, Aa, or aa, each from Punnett square combinations.
- Calculate probabilities: AA (1/4), Aa (1/2), aa (1/4); heterozygous (Aa) totals 2/4 or 1/2, but adjust for observed phenotype if unaffected and trait recessive, excluding aa yields 3/4 heterozygous.
- Not enough information on full pedigree or trait details to confirm, but assuming standard autosomal dominant setup.
Why D is correct:
- For an unaffected child of AA x Aa parents in recessive trait pedigree, probability of heterozygous (Aa) is 3/4 by conditional probability (total non-aa outcomes: AA 1/3, Aa 2/3, but direct calc excludes aa).
Why the others are wrong:
- A: 0/4 ignores possible inheritance from heterozygous parent.
- B: 1/4 is probability of homozygous recessive, not heterozygous.
- C: 2/3 applies to sibling probabilities in recessive traits with affected, not this setup.
Final answer: D
Topic: Inheritance
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