Medical Emergencies · single question
Both parents have sickle cell trait (HbAS). What is the probability that their unborn child will have sickle cell DISEASE (HbSS)?
Show answer and explanation
Correct answer: D. 25%
- A. Incorrect. 75% does not correspond to any Mendelian outcome in this cross.
- B. Incorrect. 100% disease only if both parents have sickle cell disease (HbSS × HbSS).
- C. Incorrect. 50% is the probability of the child being a CARRIER (HbAS).
- D. Correct. HbAS × HbAS Mendelian cross: HbAA (normal) = 25%, HbAS (carrier) = 50%, HbSS (disease) = 25%. Probability of sickle cell DISEASE = 25%.
Practice Medical Emergencies questions Medical Emergencies study notes