Which of the following treatment modalities can theoretically be used for the treatment of sickle cell disease(SCD)?
1. Increase the expression of the adult beta-globin genes. 2. Increase the expression of a fetal globin gene. Higher levels of Hb F are associated with reduced disease severity in patients with SCD. 3. Bone marrow transplantation. Although still experimental, gene therapy has the potential to cure SCD (a) 1 only. (b) 2 only. (c) 3 only. (d) 2 and 3. (e) All of the above.