Biology Inheritance / Variation & Genetics MDCAT 2019
PMDC Verified Question 76 of 94
A person was married to his cousin and both are heterozygous for sickle cell anemia. Among their four kids, what will be proportion of affected homozygotes?
A
50%
B
75%
C
25%
D
100%
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: 25%
Concept:

Sickle cell anemia is an autosomal recessive disorder.

Solution:

  • Both parents are heterozygous carriers (Genotype: Ss).
  • We set up a simple Mendelian cross for two heterozygotes (Ss x Ss).
  • The statistical probabilities for the offspring are:
  • SS (Normal): 25%
  • Ss (Carriers): 50%
  • ss (Affected homozygotes): 25%


Why other options are incorrect:

  • 50%: Represents the proportion of carrier offspring.
  • 75%: Represents the proportion of all phenotypically normal offspring (SS + Ss).

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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