Reproductive cloning is a type of cloning which is performed for the purpose of creating a duplicate copy of another organism. It is accomplished using a process called somatic cell nuclear transfer. In 1996, Scottish researchers announced that they had successfully cloned the first mammal, a sheep who came to be known as Dolly. Numerous other mammals have been cloned since then, and cloning has become a contentious ethical and scientific issue in some parts of the world.
In somatic cell nuclear transfer, scientists extract the nucleus of a somatic cell, a cell which can come from anywhere in the body, and insert it into an egg which has had its nucleus removed. The egg is stimulated, and it begins dividing and growing, developing into an embryo which can be implanted into a gestational surrogate and carried to term.
Some issues have developed with reproductive cloning from a scientific perspective. Clones appear to have shorter lifespans, leading to concerns about the disadvantages of cloning. There is also the risk of losing genetic diversity as a result of using cloning, especially in the agricultural industry, where the temptation to use standardized animals is understandably tempting. Like any new scientific development, cloning was heavily challenged in the scientific community when it first emerged, especially after scandals in which scientists claimed to have cloned animals but actually hadn't.
Ethically, reproductive cloning brings up some interesting issues. Some people believe that life begins at conception, and they feel that cloning is unnatural and that it could potentially violate their religious beliefs. Others are simply perturbed by the idea of being able to clone copies of living organisms, and they wonder about the risks of using cloned animals in the food supply. Psychologists and other people who study development are intrigued by the potential to use cloning as a test of the famous nature versus nurture debate.
Somatic cell nuclear transfer can also be used to create stem cell lines for therapeutic cloning, a type of cloning which is performed for medical purposes, rather than with the goal of creating a copy of another organism. It is also possible to manipulate the genetic material used in reproductive cloning using recombinant DNA technology to alter DNA.
Several nations have passed resolutions to explicitly ban human cloning, out of concern about ethical issues. Others are willing to explore the potentials of this procedure, but would prefer to see closely monitored and peer reviewed experiments which address some of the concerns about cloning.