Question

Sickle cell anemia is

• A. Characterized by elongated sickle like RBCs with a nucleus
• B. An autosomal linked dominant trait
• C. Caused by substitution of valine by glutamic acid in the $\beta$-globin chain of haemoglobin
• D. Caused by a change in a single base pair of DNA

Answer 1

The correct option is D Caused by a change in a single base pair of DNA

Sickle cell disease the haemoglobin beta gene found on chromosome 11 gets mutated. Red blood cells with normal haemoglobin are smooth and round and glide through blood vessels but in this disease, the cell becomes the sickle shape. It is caused by a single point mutation (a missense mutation) in the beta-hemoglobin gene that converts a GAG codon into GUG, which encodes the amino acid valine rather than glutamic acid. Haemoglobin transports oxygen from the lungs to other parts of the body. Thus, the correct answer is option D.