Therapeutic cloning (also known as
somatic cell nuclear transfer and cell nuclear replacement) involves taking an
egg (or
oocyte[?]) from which the nucleus has been removed, and replacing that nucleus with
DNA from the cell of another organism. The result is an
embryo with almost identical DNA to the organism. (Some people don't like to refer to the result as an embryo, since it has not been created by
fertilisation, but others think that since, given the right conditions, it could grow into a fetus and eventually a child, it doesn't seem misleading to call it an embryo). The aim of carrying out this procedure is to obtain
stem cells that are genetically matched to the donor organism. For example, if a person with
Parkinson's disease donated their DNA, the aim would be to generate embryonic stem cells that could be used to treat the condition and which would not be rejected by the patient's
immune system.
Therapeutic cloning is currently legal for research purposes in the United Kingdom, having been incorporated into the 1990 Human Fertilisation and Embryology Act in 2001. In most other countries, the practice is banned, though laws are being debated and changed regularly.