Which of the following statements about the haemoglobin in patients with sickle-cell anaemia is true?
A) Their haemoglobin is produced in greater quantities
B) Their haemoglobin is identical to that found in all individuals
C) Their haemoglobin has a different structure from normal haemoglobin
D) Their haemoglobin does not transport oxygen
E) Their haemoglobin does not undergo mutations
IMAT 2026 · Question 31
Q31 - Hereditary diseases
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The correct answer is C) Their haemoglobin has a different structure from normal haemoglobin.
Sickle-cell anaemia is caused by a point mutation in the β-globin gene: one base change (GAG → GTG) replaces glutamic acid with valine at position 6. The result is haemoglobin S, with a different structure. When it loses oxygen, it polymerises and deforms red blood cells into a sickle shape.
A) Incorrect: The problem is the structure of the haemoglobin, not the quantity produced.
B) Incorrect: Haemoglobin S differs from normal haemoglobin A by one amino acid.
C) Correct: The amino acid change gives haemoglobin S a different structure.
D) Incorrect: Haemoglobin S still carries oxygen. The damage comes from polymerisation when it is deoxygenated.
E) Incorrect: The disease is itself the result of a mutation.
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