Biology Biomolecules KMU 2024
PMDC Verified Question 17 of 142
Sickle cell anaemia results from:
A
Reduction in oxygen carrying capacity of haemoglobin
B
Linkage between the polypeptide chains
C
Single amino acid substitution in the haemoglobin molecule
D
Viral infections of RNA viruses
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Single amino acid substitution in the haemoglobin molecule
Concept:

A single typo in a massive genetic code can drastically alter the 3D structure of the resulting protein.

Solution:

  • Sickle cell anemia is the textbook example of a missense mutation disease.


  • It is caused directly by a single, catastrophic amino acid substitution. Specifically, a hydrophilic Glutamic acid is replaced by a hydrophobic Valine at position 6 on the Beta-chain of the hemoglobin molecule.


  • This tiny change causes the entire molecule to fold incorrectly, stick to other hemoglobin molecules, and warp the red blood cell into a rigid, deadly sickle shape that blocks capillaries.


Why other options are incorrect:

  • Reduction in oxygen capacity: This is the symptom/result of the sickling, not the fundamental genetic cause.


  • Viral infection: It is a strictly inherited genetic disorder, not an infectious disease.


  • Linkage between chains: Normal hemoglobin already has linkages; the disease is caused by the specific substitution, not the presence of normal linkages.

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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