A thalassemia with 2 defective genes.

A thalassemia with 2 defective genes.

• A. Thalassemia minor
• B. Hb Bart's
• C. A thalassemia trait (minor symptoms)
• D. Thalassemia major

Answer: (C)

The key idea is how gene dosage affects the severity of thalassemias. In alpha-thalassemia, each alpha-globin gene deleted reduces alpha-globin production. Deletion of two genes typically produces a mild, often asymptomatic or lightly anemic state called thalassemia trait (minor). If three alpha genes are deleted, you get HbH disease with more significant symptoms, and with all four deleted you see Hb Bart’s hydrops fetalis. So, two defective genes align with a thalassemia trait rather than a major form or fetal Hb Bart’s, making the described choice the best fit.

The key idea is how gene dosage affects the severity of thalassemias. In alpha-thalassemia, each alpha-globin gene deleted reduces alpha-globin production. Deletion of two genes typically produces a mild, often asymptomatic or lightly anemic state called thalassemia trait (minor). If three alpha genes are deleted, you get HbH disease with more significant symptoms, and with all four deleted you see Hb Bart’s hydrops fetalis. So, two defective genes align with a thalassemia trait rather than a major form or fetal Hb Bart’s, making the described choice the best fit.