Somatic Cell Gene Therapy and Germ Line Gene Therapy

There are two basic "classes" of gene therapy. Somatic cell gene therapy and germ line gene therapy.

· Somatic cell gene therapy changes/fixes/replaces genes in just one person. The targeted cells are the only ones affected, the changes are not passed on to that person's offspring.

· Germ line gene therapy makes changes in the sperm or egg of an individual. The changes that are made, adding or subtracting genes from the person's DNA, will be passed on to their offspring. This type of gene therapy raises a lot of ethical questions because it impacts the inheritance patterns of humans.

For more information, listen to Dr. Charles Link in Viewpoints.

Gene therapy can be accomplished "ex-vivo" or "in-vivo." Ex-vivo means the target cells are removed from the patient's body, the genes are fixed or replaced, and the cells are put back into the person. In-vivo means the genes are "injected" somehow, usually using a virus as a way to deliver the fixed or missing genes.