2.+What+Is+Gene+Therapy?

Gene therapy is the insertion, alteration, or removal of genes within an individual's cells and biological tissues. The genes that are responsible for the disease are removed or replaced with a 'healthy' or working gene. The goal of gene therapy is the elimination of disease.
 * What is Gene Therapy? **



The idea was first proposed in the 1970s but the first successful experiment did not take place until September 14, 1990. The experiment was done on a four-year old girl that suffered from a genetic disorder known as Severe Combined Immune Deficiency (SCID) which prevented her body from producing ADA, an enzyme necessary for the immune system. Because she lacked this enzyme, she was susceptible to many severe diseases and any virus was potentially fatal. White blood cells were extracted and genes that produce ADA were implanted into the cells and put back into the girls body. After the treatment, considerable signs of improvement in the girls immune system were noticed. However, it is not a permanent fix and she must repeat this process every few months. Trials still continue in gene therapy but most success has been seen with single gene defects such as SCID and Leber Congenital Amaurosis (LCA).
 * History **

**Two main types of gene therapy** //Somatic// gene therapy is the alteration of somatic cells (non reproductive cells). Alterations of somatic are restricted to that individual and will not be passed onto future generations. This is because the germline is not affected. Begins with an existing individual. You take an existing patient with an existing condition and you in essence try and convince her cells to manufacture the medicine she needs. Alteration of genes that do not get passed onto the persons children.

//Germline// gene therapy is the alteration of germ (sperm & egg) cells. They would tease apart the cells of an embryo and then, selecting one, they would modify some of its genes. Because the alteration is made during the embryonic stage, the genes altered would be passed down to future generations. Germline gene therapy can be done by altering the genes of a pre-embryo that carries a serious genetic defect before implantation into the mother or by altering the germ cells of an afflicted adult so that the defect does not get passed on to their offspring.

Because of the unknown effects germline therapy has on future generations, it is the most controversial.

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