Hemoglobin that causes most common variety of nondeletional ?-thalassemia, which is most prevalent in soulhern China and Southeast Asia, esp. Laos. Gene arises from point mutation (TAA?CAA) in termination codon of ?2 globin gene. Anemia in homozygotes is more severe than in heterozygotes (thalassemia minor). Condition is also marked by reticulocytosis and hepatosplenomegaly.