NEET 2026 (Phase 1) · BiologyPrevious Year Question
The sixth mutant codon of beta globin gene causing polymerization of Haemoglobin and change in RBC shape is ______.
- A.GUG✓
- B.AUG
- C.GAG
- D.CAG
Correct Answer
(A) GUG
Solution & Explanation
Answer: (A) GUG Solution: In sickle-cell anaemia, a single base substitution at the sixth codon of the beta globin gene changes the codon from GAG to GUG, which codes for Valine instead of Glutamic acid. The resulting mutant haemoglobin polymerises under low oxygen tension and changes the RBC shape from biconcave to sickle-shaped. Hence the mutant sixth codon is GUG. NCERT Reference: NCERT Class XII, Ch 4, p.75, lines 5-9: "protein results due to the single base substitution at the sixth codon of the beta globin gene from GAG to GUG. The mutant haemoglobin molecule undergoes polymerisation under low oxygen tension causing the change in the shape of the RBC from biconcave disc to elongated sickle like structure"
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