Individuals have 1 defective B-globin gene and mild symptoms.

• A. Iron deficiency anemia
• B. Thalassemia major
• C. Thalassemia minor
• D. Sickle cell disease

Answer: (C)

A single defective beta-globin gene causes beta-thalassemia trait (minor). When only one beta-globin gene is mutated, beta-globin production is reduced but not absent, leading to a mild imbalance of globin chains and a mild, often asymptomatic microcytic anemia. This condition is inherited in an autosomal recessive pattern, and patients typically have low hemoglobin with a small drop in mean corpuscular volume, but normal or near-normal iron status. Hematology often shows elevated HbA2 (and sometimes HbF) on electrophoresis, reflecting the compensatory rise in other beta-like hemoglobins. This explains the mild symptoms and laboratory findings characteristic of thalassemia minor. In contrast, thalassemia major requires two defective beta-globin genes and presents with severe anemia early in life, while sickle cell disease stems from a specific beta-globin mutation (HbS) with distinct clinical features such as vaso-occlusive crises. Iron deficiency anemia would not be due to a beta-globin gene defect.