Thalassemia is classified into two based on the globin gene defect: alpha-thalassemia (Hemoglobin Subunit Alpha 1: HBA1 and Hemoglobin Subunit Alpha 2: HBA2 genes) and beta-thalassemia (Hemoglobin Subunit Beta: HBB gene). Here, HBA1 is linked to Alpha-thalassemia.