Animal reproductive technologies — the signs of cloning — have been thoroughly studied for decades. The U.S. Food and Drug Administration analyzed over 400 scientific studies on cloning, conducted over many years and including several generations and large families of livestock. The National Academy of Sciences has also studied this topic, publishing reviews in 2002 and 2004.
Process of Cloning
The most common cloning method, known as "somatic cell nuclear transfer" or simply "nuclear transfer," requires two kinds of cell. One is a somatic cell, which is collected from the animal that is to be cloned. A somatic cell is any cell other than a sperm cell or egg cell, and contains the complete DNA of the animal it came from. For cloning purposes, somatic cells are typically found by a routine skin surgery made by a vet.
The other kind of cell required for cloning is an egg cell, which is collected from a female of the same species. In the lab, a scientist extracts and discards the nucleus of the egg cell, which is the part of the cell that contains the egg donor's genes. The scientist then inserts the somatic cell from the genetic donor into the egg and "fuses" the two with electricity. The resulting fused egg contains the genetic donor's DNA.
The scientist stimulates the fused egg, which "activates" the egg and causes it to divide just as an egg would if it had been fertilized by a sperm cell in conventional reproduction. The activated egg is then placed in a culture medium. As cellular division continues over the course of several days, a blastocyst forms. After about a week, an embryo transfer specialist transfers the blastocyst to a recipient female where it continues to develop. After a full-term pregnancy, the recipient gives birth to an animal that is essentially the identical twin of the genetic donor.
Animal cloning has been rapidly improving livestock herds for more than two decades and has been an important tool for scientific researchers since the 1950s. Although the 1997 entrance of Dolly the cloned sheep was a worldwide media event, animal cloning was not altogether new. Dolly was considered a scientific breakthrough not because she was a clone, but because the source of the genetic material used to produce Dolly was an adult cell, not a primary one.
There are two ways to make an exact genetic copy of an organism such as a sheep or a laboratory mouse, Embryo Splitting and Somatic cell nuclear transfer.