Therapeutic Cloning

Therapeutic cloning produces embryonic stem cells that are genetically matched to a patient. Its scientific name is somatic cell nuclear transfer (SCNT).The steps are:
1. The nucleus is removed from a donated egg cell, leaving an enucleated egg.
2. The nucleus of a somatic (body) cell, such as a skin cell, is taken from the patient and inserted into the enucleated egg.
3. A small electric shock stimulates the cell to start dividing by mitosis, as a zygote would.
4. After about five days it has developed into a blastocyst.
5. Embryonic stem cells are removed from the inner cell mass and grown in culture.
6. The stem cells are stimulated to differentiate into the tissue the patient needs.Because the nucleus came from the patient, the stem cells carry the patient's own nuclear DNA and make the same cell-surface antigens. Tissue made from them should not be rejected by the immune system, so no immunosuppressant drugs are needed.Therapeutic cloning must be distinguished from reproductive cloning. In reproductive cloning, the cloned embryo is implanted into a uterus and allowed to develop into a new individual, as with Dolly the sheep in 1996. In therapeutic cloning the embryo is never implanted; it is used only as a source of stem cells, and is destroyed when they are removed.