Cloning

       Cloning is the process of creating an identical copy of an organism or thing by DNA cloning, reproductive cloning, or therapeutic cloning. When scientists are studying a gene, they will sometimes use bacterial plasmids (DNA molecules recreating themselves) to produce copies of that gene. To clone a gene, A DNA fragment containing the gene is moved apart from the chromosomal DNA (containing most of the genes) using special enzymes and then is mixed with a plasmid cut by the same type of enzyme. This process is called the DNA cloning. When an animal is cloned by using the same DNA as an animal currently living or previously died, it is known as reproductive cloning. To start the cloning process, the DNA is taken from the previously or currently living animal's adult's cell's nucleus to a reconstructed egg's nucleus. To start the cell division and the development of the embryo, chemicals must be added to the egg. The egg is put inside a living female's body to which the DNA relates to when it grows to a suitable age. After a certain amount of time, the embryo is born as a baby. The first reproductive cloned animal cloned from adult DNA was Dolly the sheep. She was just like a normal sheep until she died after suffering from crippling arthritis and lung cancer at six years of age in 2003.
       Therapeutic cloning is when human embryos are produced for further research. This process of cloning is not not clone human beings but to treat diseases and study human development. After five days of cell division, the stem cells are taken out of the egg, destroying the embryo.
       Although cloning is ingenious, it fails 90% of the time and even when it succeeds, the cloned animal has birth defects and is more vulnerable to infections. Cloning of humans is strictly advised against and may even be banned in the future due to its dangerous risk taking.

http://www.sfgate.com/cgi-bin/article.cgi?file=/chronicle/archive/1999/05/15/MN82186.DTL