Question
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 ?
NEET
Zoology
Principles of Inheritance and Variation
2026
NEET 2026 (Cancelled)
NEET Zoology Question (2026) — Solution
Options
- A. Thalassemia
- B. Sickle-cell anaemia
- C. Phenylketonuria
- D. Haemophilia
Answer
B. Sickle-cell anaemia
Step-by-step solution
Sickle-cell anaemia is an autosomal recessive genetic disorder caused by a point mutation in the DNA sequence of the gene encoding the beta globin chain of haemoglobin. This mutation results in the substitution of Glutamic acid (Glu) by Valine (Val) at the sixth position of the beta globin chain. The codon GAG (for Glutamic acid) is replaced by GUG (for Valine). Thalassemia is a quantitative defect in globin chain synthesis, Phenylketonuria is an inborn error of metabolism affecting phenylalanine breakdown, and Haemophilia is a sex-linked blood clotting disorder. Answer: Sickle-cell anaemia
Related: Zoology — Principles of Inheritance and Variation · All PYQ Banks