Which one of the following disorders is caused by the substitution of Glutamic acid (Glu) by Valine (Val) at the sixth position of the beta globin chain of the haemoglobin molecule?
Answer: (B) Sickle-cell anaemia. Answer: (B) Sickle-cell anaemia Solution: Sickle-cell anaemia is caused by the substitution of the amino acid Glutamic acid (Glu) by Valine (Val) at the sixth position of the beta globin chain of haemoglobin.
- A.Thalassemia
- B.Sickle-cell anaemia✓
- C.Phenylketonuria
- D.Haemophilia
Correct Answer
(B) Sickle-cell anaemia
Solution & Explanation
Answer: (B) Sickle-cell anaemia Solution: Sickle-cell anaemia is caused by the substitution of the amino acid Glutamic acid (Glu) by Valine (Val) at the sixth position of the beta globin chain of haemoglobin. This single amino acid change results from a point mutation and alters the haemoglobin molecule. Thalassemia, phenylketonuria and haemophilia have different molecular bases. NCERT Reference: NCERT Class XII, Ch 4, p.75, lines 3-4: "(Glu) by Valine (Val) at the sixth position of the beta globin chain of the" (continuation of "The defect is caused by the substitution of Glutamic acid" on p.74, line 27)