Beta-thalassemia major occurs in individuals who are

Beta-thalassemia major occurs in individuals who are

• A. Homozygous for defective B-globin gene
• B. Heterozygous
• C. Silent carrier
• D. Compound heterozygous

Answer: (A)

Beta-thalassemia major is produced when both beta-globin genes carry defective mutations, so beta-globin production is severely reduced or absent. With no functional beta chains, the balance of globin chains is disrupted, leading to predominantly ineffective erythropoiesis, marked microcytic hypochromic anemia, and compensatory bone marrow expansion. If only one beta-globin gene is mutated, the person typically has beta-thalassemia trait with milder anemia, not major. Silent carriers show no hematologic symptoms. While having two different beta-globin mutations (compound heterozygosity) can also produce a major phenotype in some cases, the classic and most straightforward scenario described here is homozygous defective beta-globin genes.

Beta-thalassemia major is produced when both beta-globin genes carry defective mutations, so beta-globin production is severely reduced or absent. With no functional beta chains, the balance of globin chains is disrupted, leading to predominantly ineffective erythropoiesis, marked microcytic hypochromic anemia, and compensatory bone marrow expansion. If only one beta-globin gene is mutated, the person typically has beta-thalassemia trait with milder anemia, not major. Silent carriers show no hematologic symptoms. While having two different beta-globin mutations (compound heterozygosity) can also produce a major phenotype in some cases, the classic and most straightforward scenario described here is homozygous defective beta-globin genes.