Public interest in cloning began in 1997, when Dolly the sheep was born. Dolly was the first animal ever produced by artificial cloning. Her birth was a major breakthrough in the field of biotechnology -- and the achievement did not go unnoticed by lawmakers. It seems that nearly every month since, advancements have been made in cloning technology, and legislation has been proposed or passed in an attempt to control it. Not surprisingly, these regular announcements continue to fuel the enthusiasm of some and the fears of others.

Cloning technology, like many technologies, can be applied in a variety of ways and for a variety of reasons -- some sound and some not so sound. The two most important applications of cloning, and those most often reported in the media, are reproductive cloning and therapeutic cloning. In general, reproductive cloning is the one that evokes fear and disgust, while therapeutic cloning elicits a great deal of enthusiasm. So, what is the difference between these two cloning applications?

The goal of therapeutic cloning is to produce cloned embryos as a source of stem cells. These amazing cells have the potential to become any type of cell in your body -- nerve cells, heart cells, liver cells. The important advantage of using cloned embryos over naturally produced embryos is that the tissues produced from the clone's stem cells are perfectly matched to the individual who donated the cell that produced the clone. That's because the cloned embryo contains an exact copy of the DNA of the person who donated the cell. Organs produced in this way are unlikely to be rejected by the recipient's body, a serious problem in organ transplant procedures.

Unlike therapeutic cloning, which does not allow the cloned embryo to progress beyond a certain stage, the goal of reproductive cloning (which, in 2002, had not yet been performed with humans) is to create a fully formed individual. However, just like an embryo cloned for therapeutic use, a cloned individual carries the DNA of only one parent. The reasons some people give for wanting to reproductively clone humans range from the desire to avoid passing on diseases for which they are carriers, to wanting to avoid the unknowns associated with sperm banks. Those who oppose the idea often suggest that it is unethical for individuals to cheat mortality by creating carbon copies of themselves and that it's just not "natural."

While most scientists have little concern over a population of carbon copies, many argue that reproductive cloning is unsafe. Indeed, the technology is so new that it is still overwhelmingly unsuccessful. Its success rate, at best, is one live birth for every 75 attempts -- a rate that some scientists think suggests a deeper problem with the technology, a problem that could adversely affect the long-term health of cloned animals. Only time will tell.