Figure 1. Gene therapy attempts to correct disease by introducing genetic material into cells. A dysfunctional gene can be corrected by the introduction of a normal copy of the gene (top panel). Many different diseases, both genetic and acquired, can be targets for gene therapy (middle panel). Viruses can be used as agents to transfer genetic material into human cells (bottom panel). CF: cystic fibrosis; HIV: human immunodeficiency virus.

Figure 2. Two different methods can be used to introduce genetic material into the body. Ex vivo therapy involves the removal of cells from the patient and transfer of the gene into the cells outside of the body. The cells are then returned to the patient to correct disease. For in vivo gene transfer, the vector carrying the gene is directly injected into the body. Once in the body, the vector must transfer the genetic material to the appropriate cells in order to correct disease.