What genetic disorder is characterized by the substitution of valine for glutamic acid in hemoglobin?

Sickle cell disease is characterized by a specific mutation in the gene that encodes the beta chain of hemoglobin. In this disorder, the DNA sequence that normally codes for glutamic acid is altered so that valine is substituted for glutamic acid at the sixth position of the beta globin chain. This single nucleotide change leads to the production of abnormal hemoglobin known as hemoglobin S (HbS).

The altered structure of hemoglobin in sickle cell disease causes red blood cells to take on a rigid, sickle-like shape, particularly when the blood is deoxygenated. This distortion leads to various complications, including pain crises, increased risk of infection, and possible organ damage due to impaired blood flow.

In contrast, thalassemia is caused by mutations that affect the production of globin chains, leading to an imbalance that results in ineffective erythropoiesis and anemia. Cystic fibrosis is due to mutations in the CFTR gene, affecting chloride ion transport, and hemophilia is related to mutations affecting clotting factors, specifically factor VIII or IX. None of these conditions involve the substitution of valine for glutamic acid in hemoglobin.