Cloning Fast Facts

Dolly the Sheep, the world's first cloned mammal, is shown in this undated photo. Veterinarians gave Dolly a lethal injection February 14, 2003 at Scotland's Roslin Institute after they discovered signs of progressive lung disease.

(CNN)Here's some background information about cloning, a process of creating an identical copy of an original.

Reproductive Cloning is the process of making a full living copy of an organism. Reproductive cloning of animals transplants nuclei from body cells into eggs that have had their nucleus removed. That egg is then stimulated to divide using an electrical charge and is implanted into the uterus of a female.
Therapeutic Cloning is the process where nuclear transplantation of a patient's own cells makes an oocyte from which immune-compatible cells (especially stem cells) can be derived for transplant. These cells are stimulated to divide and are grown in a Petri dish rather than in the uterus.
Gene Cloning creates copies of genes or DNA fragments. Gene cloning is the most common form of cloning performed by researches at the National Human Genome Research Institute. Genes are cloned for scientists to study in a laboratory setting.
    1952 - Scientists demonstrate they can remove the nucleus from a frog's egg, replace it with the nucleus of an embryonic frog cell, and get the egg to develop into a tadpole.
    1984 - A researcher in Britain claims that he has cloned the first mammal, a lamb that was produced via the nuclear transfer of sheep embryo cells.
    2000 - Pigs and a goat are rep