now been successfully cloned from adult or fetal cells, and attempts are being made (so far without success) to clone monkeys, dogs, horses, and other animals in the same way. The cloning of mammals involves a process called nuclear transplantation or somatic cell nuclear transfer (SCNT). In biological terminology, clones are not replicas of each other, but contain identical genetic material.

The nuclear transplantation procedure is also used for a purpose distinctly different from cloning whole mammals. Like reproductive cloning, the process of nuclear transplantation to produce stem cells (also called “therapeutic cloning, nonreproductive cloning, or research cloning”) involves placing the DNA from one mammal into an enucleated egg (an egg from which the chromosomes have been removed). Thereafter, the egg is stimulated to divide. At the blastocyst stage of embryonic development (in humans, a 5-7 day old preimplantation embryo of about 150 cells), its inner cell mass is harvested and grown in culture for subsequent derivation of embryonic stem cells. These cells are then used for scientific and clinical investigations. Neither the cells nor the blastocyst are ever implanted in a uterus, as is required for reproductive cloning and the birth of an animal. Figures 1 and 2 in the Executive Summary illustrate the differences between the techniques of reproductive cloning and nuclear transplantation to produce stem cells.

This report, by a joint panel of the National Academies Committee on Science, Engineering, and Public Policy (COSEPUP) and the National Academies Board on Life Sciences (BLS), focuses on issues raised by the possible application of nuclear transplantation technology to the reproductive cloning of humans.

In 1997, after a report announced the cloning experiments that produced Dolly the sheep [1], President Clinton asked that the National Bioethics Advisory Commission (NBAC), chaired by Harold Shapiro, look at the issue of human cloning. The NBAC’s report, Cloning Human Beings [2], came to various conclusions, including the following (emphasis added):

“The Commission concludes that at this time it is morally unacceptable for anyone in the public or private sector, whether in a research or clinical setting, to attempt to create a child using somatic cell nuclear transfer cloning. The Commission reached a consensus on this point because current scientific information indicates that this technique is not safe to use in humans at this point. Indeed, the Commission believes it would violate important ethical obligations were clinicians or researchers to attempt to create a child using these particular technologies, which are