Class 12 NEET Biology Principles of Inheritance and Variation Questions Part 3

Sickle cell anemia is caused by a single nucleotide mutation in the beta-globin gene, which is a part of hemoglobin. This mutation causes the amino acid glutamic acid to be replaced by valine at the sixth position of the beta-globin chain. The resulting hemoglobin, called hemoglobin S, can deform red blood cells into a sickle shape, especially under low oxygen conditions. This change can cause various complications including pain, anemia, and increased risk of infection.
The other disorders listed - Thalassemia, Haemophilia, and Phenylketonuria - are also genetic disorders, but they are caused by different mutations.