Tuesday, March 11, 2008


It is unfortunate that the term "cloning" refers to three very different procedures with three very different goals. It is also unfortunate that the first thought many people have when they hear the term is of horror movies which have showed the creation of human monsters or of armies of superhuman soldiers with subhuman brains. The reality of cloning is very different.

The three different types of "cloning" are:

bulletEmbryo cloning: This is a medical technique which produces monozygotic (identical) twins or triplets. It duplicates the process that nature uses to produce twins or triplets. One or more cells are removed from a fertilized embryo and encouraged to develop into one or more duplicate embryos. Twins or triplets are thus formed, with identical DNA. This has been done for many years on various species of animals; only very limited experimentation has been done on humans.

bulletAdult DNA cloning (a.k.a. reproductive cloning) This technique which is intended to produce a duplicate of an existing animal. It has been used to clone a sheep and other mammals. The DNA from an ovum is removed and replaced with the DNA from a cell removed from an adult animal. Then, the fertilized ovum, now called a pre-embryo, is implanted in a womb and allowed to develop into a new animal. As of 2002-JAN, It had not been tried on humans. It is specifically forbidden by law in many countries. Based on previous animal studies, it also has the potential of producing severe genetic defects. For the latter reason alone, many medical ethicists consider it to be a profoundly immoral procedure when done on humans.
bulletTherapeutic cloning (a.k.a. biomedical cloning): This is a procedure whose initial stages are identical to adult DNA cloning. However, the stem cells are removed from the pre-embryo with the intent of producing tissue or a whole organ for transplant back into the person who supplied the DNA. The pre-embryo dies in the process. The goal of therapeutic cloning is to produce a healthy copy of a sick person's tissue or organ for transplant. This technique would be vastly superior to relying on organ transplants from other people. The supply would be unlimited, so there would be no waiting lists. The tissue or organ would have the sick person's original DNA; the patient would not have to take immunosuppressant drugs for the rest of their life, as is now required after transplants. There would not be any danger of organ rejection.

There are major ethical concerns about all three types of cloning, when applied to humans.

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