The extent to which researchers are allowed to conduct experiments using human embryonic stem cells, a cluster of about 30 cells that form inside an embryo about five days after fertilization, is a matter legislators will have to decide in the coming months. At this stage, the embryo, or blastocyst, is the size of a pinhead, but the stem cells carried inside have the remarkable ability to transform into virtually any mature human cell, such as heart, muscle, nerve and liver cells. Because of their versatility, many scientists believe that stem cells could be used to replace defective cells in people with all types of ailments and injuries, including Alzheimer's Disease, Parkinson's Disease, Diabetes, spinal cord injuries and other incurable ailments.

On Aug. 9, 2001, President Bush announced that federal funds would be restricted to research on 64 existing embryonic stem cell lines obtained from frozen embryos donated by infertile couples. These excess embryos were produced at in vitro fertilization (IVF) clinics, and, because they were no longer needed for pregnancy, were destined for destruction. Henceforth, the president said, millions of other frozen embryos now sitting in IVF clinics would be off limits to federal research dollars. In August 2001, Bush also announced the formation of the 17-member President's Council on Bioethics, which makes legislative recommendations for regulating this research.

A key element in the stem cell debate is the opposition to the cloning of human beings. While most scientists oppose reproductive cloning, there is widespread support for a technique called somatic cell nuclear trransfer commonly referred to as therapeutic cloning. This technique begins by removing the nucleus, which contains DNA, from a woman's egg, and replacing it with DNA from a body, or somatic cell, donated by a patient. The anticipated result would be a cloned embryo that is genetically similar to the patient, which decreases the possibility of rejection of the implanted healthy cells. With therapeutic cloning, the stem cells would be harvested by the fifth day, thereby destroying the cloned embryo before it could be implanted in the uterus.

Researchers assert that cloned stem cells could be invaluable for treating disease in humans. Legislators across political parties have entered into the debate of regulating this new field of study. Governor Gray Davis of California signed a bill approving therapeutic cloning in the state. Senators Dianne Feinstein (D-California.), Edward Kennedy (D-Massachusetts) and Orrin Hatch (R-Utah) have proposed similar legislation in the U.S. Senate, while Senator Sam Brownback (R-Kansas) has authored a bill that would criminalize all human cloning. The House of Representatives has already passed a bill similar to the one proposed by Senator Brownback.