Physiology & Biochemistry · single question
Both parents carry the sickle cell trait (each is heterozygous). What is the chance any given child will have sickle cell DISEASE?
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Correct answer: A. 25%
- A. Correct. Sickle cell is autosomal recessive. Two carriers (Aa × Aa) → 25% affected (aa), 50% carriers (Aa), 25% unaffected (AA).
- B. 50% is the chance of being a CARRIER, not of having the disease.
- C. 75% is the chance of having at least one normal allele (not affected) reversed; not the affected fraction.
- D. 100% would require both parents to be affected (aa × aa).
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