Reproductive and Therapeutic Cloning

The term clone—derived from the Greek word klon, which means “twig”—refers to any individual or group of genetically identical cells or organisms that descend from a single common ancestor. The possibility of cloning a human being from a progenitor who has already been born came closer to reality when Ian Wilmut and colleagues at the Roslin Institute in Scotland announced the birth of the first cloned mammal—a sheep named Dolly—in 1996. This accomplishment is [Page 976]an example of reproductive cloning, resulting in the live birth of a cloned organism. More directly related to human embryonic stem cell (hESC) research is what is termed therapeutic cloning, the purpose of which is to create embryos in order to derive hESCs for potentially therapeutic research purposes or to ...