As cells mature, many genes become permanently inactive. The pattern of active and inactive genes in a cell and the resulting protein composition determine what kind of cell it is and what it can and cannot do. Flaws in genes can result in disease. Advances in understanding and manipulating genes have set the stage for scientists to alter patients' genetic material to fight or prevent disease. Gene therapy is an experimental medical intervention that involves modifying the genetic material of living cells to fight disease.
Gene therapy is still experimental.
One of the goals of gene therapy is to supply cells with healthy copies of missing or altered genes. Instead of giving a patient a drug, doctors attempt to correct the problem by altering the genetic makeup of some of the patient's cells. Examples of diseases that could be treated this way include cystic fibrosis and hemophilia. In general, a gene cannot be directly inserted into a person's cell. The most common types of vectors used in gene therapy are viruses.