Gene therapy mainly involves the use of DNA for pharmaceutical purposes. In gene therapy, DNA is used to either to supplement or to alter genes in cells as a therapy for treating diseases. The procedure mainly involves insertion of a normal gene into an organism in order to correct a genetic defect. It may also involve the replacement of an absent or faulty gender with a normal functional gene. The procedure has been safely implemented in fruit flies and mice. In 1990, it was tested on the first patient, Ashanthi Desilva who was injected with a healthy ADA gene. Despite the success of gene therapy in various cases, there is a debate on whether it should be used or not. Gene therapy has its own shortcoming like rejection of new genes, the permanence of therapy, and many others. Although it has been opposed on ethical, moral, and scientific grounds, gene therapy should be used in reverting genetically-prone diseases saving people from diseases like cancer.