For both reproductive cloning and stem cell production, a reconstructed egg cell produced by nuclear transplantation is stimulated to cause it to begin dividing. If that is successful, several sequential cell divisions can give rise to the preimplantation embryo known as a blastocyst that is composed of 64-200 cells (see Figure 2).

It is at this stage that the procedures used for reproductive cloning and for nuclear transplantation to produce stem cells become entirely different. In reproductive cloning, a blastocyst formed by the nuclear transplantation procedure is implanted in a uterus, where it begins the process of forming a fetus. Any animals produced in this way will have the same nuclear genes as the adult cells used to produce them, and when the nuclei from several somatic cells from a single animal are transferred to a series of eggs, all the animals born are said to be “clones” of the original adult animal.

Although these clones will be physically very similar, the animals will not be physically or behaviorally identical, because of various factors, including their different uterine and postnatal environments and experiences.

In nuclear transplantation to produce stem cells, cells are isolated from the blastocyst 4-5 days after the procedure, and the cells are used to make a stem cell line for further study and clinical applications. Neither the blastocyst nor the stem cells are ever placed into a uterus. Moreover, as described in Chapter 2, human stem cells do not themselves have the capacity to form a fetus or a newborn animal. Nevertheless, in the popular press and other media, the term “human cloning” has often been misleadingly applied to both this procedure and reproductive cloning whenever either is proposed to be used in a human context.

As part of our panel’s charge, we were asked, “Based on the current scientific and medical evidence, should there be a moratorium on the cloning of a person? What are the implications of doing so? Of not doing so?” This raises the question of the implications that a ban on human reproductive cloning could have for the very different process of nuclear transplantation to produce stem cells.

None of the findings summarized in the preceding section that support the panel’s conclusions regarding a ban on human reproductive cloning would support a ban on the use of the nuclear transplantation technology to produce stem cells. A recent report prepared by a different committee of the National Academies has emphasized that there is a great potential for studies on stem cells isolated through nuclear transplantation to increase the understanding and potential treatment of various diseases and debilitating disorders, as well as fundamental biomedical knowledge. The diseases and debilitating disorders include “Lou Gehrig’s disease” (amyotrophic lateral sclerosis, or ALS), Parkinson’s disease, Alz-

Front Matter (R1-R22)

Executive Summary (1-18)

1. Introduction (19-23)

2. Cloning: Definitions and Applications (24-38)

3. Animal Cloning (39-60)

4. Assisted Reproductive Technology (61-73)

5. Human Reproductive Cloning: Proposed Activities and Regulatory Context (74-91)

6. Findings and Recommendations (92-100)

Appendix A: Panel and Staff Biographical Information (101-110)

Appendix B: Animal Reproductive Cloning Data Tables on Reproductive Cloning Efficiency and Defects (111-143)

Appendix C: Workshop Agenda and Speaker Biographical Information (144-153)

Appendix D: Bibliography (154-258)

Appendix E: Glossary (259-272)