added genetic material, if it produces pathology, instead disrupts regulatory functions enough to produce anemia. Hemoblogin's normal alpha and beta subunits each have an iron-containing central portion (heme) that allows the protein chain of a subunit to fold around it. Normal adult hemoglobin contains 2 alpha and 2 beta subunits. Thalassemias typically affect only the mRNAs for production of the beta chains (hence the name). Since the mutation may be a change in only a single base (single-nucleotide polymorphism), on-going efforts seek gene therapies to make that single correction. Risk factors Family history and ancestry are factors that increase the risk of beta thalassemia. Depending on family history, if a person's parents or grandparents had beta thalassemia major or intermedia, there is a 75% (3 out of 4) probability (see inheritance chart at top of page) of the mutated gene being inherited by an offspring. Even if a child does not have beta thalassemia major or intermedia, they can still be a carrier, possibly resulting in future generations of their offspring having beta thalassemia. Another risk factor is ancestry. Beta thalassemia occurs most often in people of Italian, Greek, Middle Eastern, Southern Asian, and African ancestry. Diagnosis Abdominal pain due to hypersplenism, splenic infarction and right-upper quadrant pain caused by gallstones are major clinical manifestations. However, diagnosing thalassemia from symptoms alone is inadequate. Physicians note these signs as associative due to this disease's complexity. The following associative signs can attest to the severity of the phenotype: pallor, poor growth, inadequate food intake, splenomegaly, jaundice, maxillary hyperplasia, dental malocclusion, cholelithiasis, systolic ejection murmur in the presence of severe anemia and pathologic fractures. Based on symptoms, tests are ordered for a differential diagnosis. These tests include complete blood count; hemoglobin electrophoresis; serum transferrin, ferritin, total iron-binding capacity; urine urobilin and urobilogen; peripheral blood smear, which may show codocytes, or target cells; hematocrit; and serum bilirubin. The expected pattern on hemoglobin electrophoresis in people with beta-thalassemia is an increased level of hemoglobin A2 and slightly increased hemoglobin F. The diagnosis is confirmed with hemoglobin electrophoresis or high performance liquid chromatography. Skeletal changes associated with expansion of the bone marrow: Chipmunk facies: bossing of the skull, prominent malar eminence, depression of the bridge of the nose, tendency to a mongoloid slant of the eye, and exposure of the upper teeth due to hypertrophy of the maxillae. Hair-on-end (or "crew cut") on skull X-ray: new