In which disorder change of single base pair in the gene for beta globin chain results in change of glutamic acid to valine?
Answer: (D) Sickle cell anaemia. Answer: (D) Sickle cell anaemia Solution: Sickle cell anaemia results from a single base substitution (point mutation) in the beta globin gene (codon GAG to GUG), which substitutes glutamic acid (Glu) by valine (Val) at the sixth position of the beta globin chain.
- A.Haemophilia
- B.Phenylketonuria
- C.Thalassemia
- D.Sickle cell anaemia✓
Correct Answer
(D) Sickle cell anaemia
Solution & Explanation
Answer: (D) Sickle cell anaemia Solution: Sickle cell anaemia results from a single base substitution (point mutation) in the beta globin gene (codon GAG to GUG), which substitutes glutamic acid (Glu) by valine (Val) at the sixth position of the beta globin chain. This precisely matches the description, so sickle cell anaemia is the answer; the other disorders do not involve this Glu-to-Val change. NCERT Reference: NCERT Class XII, Ch 4, p.74-75, p.75 lines 3-6: "(Glu) by Valine (Val) at the sixth position of the beta globin chain of the haemoglobin molecule. The substitution of amino acid in the globin protein results due to the single base substitution at the sixth codon of the beta globin gene from GAG to GUG."