gene therapy

Introduction of a normal gene into an individual in whom that gene is not functioning, either into those tissue cells that normally express the gene (curing that individual only) or into an early embryonic cell (curing the individual and all future offspring). Prerequisites for each procedure include finding the best delivery system (often a virus) for the gene, demonstrating that the transferred gene can express itself in the host cell, and establishing that the procedure is safe. Diseases for which gene-therapy research is advanced include cystic fibrosis, Huntington's disease, and familial hypercholesterolemia; research continues on its application for Alzheimer's disease, breast and other cancers, and diabetes. Some aspects of gene therapy, including genetic manipulation and selection, research on embryonic tissue, and experimentation on human subjects, have aroused ethical controversy.