Outline the process of gene therapy using a named example.

Gene therapy is defined as a set of strategies or procedures that uses Recombinant DNA technology to insert DNA into a patient in order to correct a genetic disease. The result is an altered genotype where the abnormal gene is corrected. The process is still very experimental. In a genetic disease where the allele of a gene is recessive, adding the dominant allele to the patient could prevent the disease. An example is to prevent SCID (severe combined immune deficiency) caused by lack of the enzyme ADA, which produces lymphocytes that help the body fight diseases. The SCID encoded gene is recessive. The process would include: 1) screening a baby to identify whether it has SCID. 2) Obtaining the ADA encoded gene and inserting it into a retrovirus. 3) Mixing the retrovirus with stem cells. This causes the ADA gene to enter the stem cell's chromosomes. 4) The stem cells (now containing ADA) are injected back into the baby's blood stream.