Which genetic disorder causes abnormal hemoglobin resulting in sickle-shaped red blood cells?

• A. Sickle cell anemia
• B. Thalassemia
• C. Hemophilia
• D. Cystic fibrosis

Answer: (A)

A genetic change in the beta-globin gene produces abnormal hemoglobin called HbS. When oxygen levels drop, HbS tends to polymerize, causing red blood cells to deform into a sickle shape. These stiff, misshapen cells break down more quickly and can clog small vessels, leading to pain episodes and anemia. Sickle cell disease is inherited in an autosomal recessive pattern, so having two mutated copies causes the disease, while one copy typically results in a milder trait.

The other options describe different problems: thalassemia involves reduced production of globin chains and doesn’t inherently cause sickling; hemophilia is a clotting-factor deficiency; cystic fibrosis is a chloride-channel defect. None of these produce sickle-shaped red blood cells.