History of Cloning

The term "cloning" is actually a general term used for three seperate kinds of procedures, which have different purposes. These types of cloning are embryo cloning, adult DNA cloning, and therapeutic cloning. Embryo Cloning is also called "artificial twinning" because it uses the same process by which twins naturally develop. Embryo cloning has been used in mice experiments as early as the late 1970's. Pro-life activists with a large amount of political influence had research on this type of cloning restricted in the United States and in some other countries in the 1980's. When President Clinton came into office, the ban on public funding for human embryo and fetal research was lifted. Robert J. Stillman and his team were the first to publically announce human cloning of this kind. They successfully split flawed human embryos that had no chance of survival, mostly to see how the public would react to human cloning. The National Institute of Health developed guidelines by which cloning researchers must abide. Human adult cloning uses DNA extracted from an adult organism to replace the DNA in an embryo. The embryo then grows naturally into a genetically identical adult. This kind of cloning was assumed impossible for mammals until the British scientist Ian Wilmut produced a cloned sheep named Dolly in 1996. In 1998, scientists at a Hawaiian university recloned already cloned mice and Japanese researchers cloned calves. Also in Japan, scientists claimed to have successfully cloned a human until the embryo reached the fourth cell stage at which time it was destroyed. This created a tremendous amount of controversey. Finally, therapeutic cloning follows the same procedure as human adult cloning until the embryo has grown for about fourteen days. At this time, the stem cells would be extracted and encouraged to grow into organs for transplantation. The first successful therapuetic cloning was accomplished in 2002. By the end of the year 2000, eight species of mammals had been cloned including mice, cows, rhesus monkeys, sheep, goats, pigs, and rats. Between 3,000 and 5,000 cloned animals have been produced to date.

Navigation

Home
Process of Cloning