Answer to Question 1
ANS: C
The osmotic fragility is not useful in differentiating the various forms of thalassemia from one another. Hemoglobin electrophoresis is an important tool for differentiating them, whereas CBC results and clinical findings vary depending on the severity of the thalassemic syndrome present and so can be useful.
Answer to Question 2
ANS: D
Hb S is a structurally abnormal b globin chain; this gene is inherited from one parent. The b0 gene is inherited from the other parent, which means that no b chain production occurs from that gene. Thus the patient will not have any normal b chains to combine with a chains and form Hb A. The patient will have primarily Hb S, with an elevated Hb F, which is the same pattern seen in homozygous Hb S (i.e., sickle cell anemia). However, in sickle cell anemia the red cells are normocytic, whereas in Hb S b0thalassemia the red cells will be microcytic.
