Appendix N. 
The Biology of Nuclear Cloning and the Potential of 
Embryonic Stem Cells for Transplantation Therapy 
RUDOLF JAENISCH, M.D. 
Whitehead Institute, 9 Cambridge Center, Cambridge, MA 
SUMMARY 
An emerging consensus is that somatic cell nuclear transfer 
(SCNT) for the purpose of creating a child (also Ccdled "reproductive 
cloning") is not acceptable for both moral and scientific reasons. In 
contrast, SCNT with the goal of generating an embryonic stem cell 
line ("therapeutic cloning”) remains a controversial issue. Although 
therapeutic cloning holds the promise of yielding new ways of 
treating a number of degenerative diseases, it is not acceptable to 
many because the derivation of an embryonic stem cell line from the 
cloned embryo (an essential step in this process) necessarily involves 
the loss of an embryo and hence the destruction of potential human 
life. 
In this article, I will develop two main arguments that are based 
on the available scientific evidence. 1) In contrast to sin embryo 
derived by in vitro fertilization (IVF), a cloned embryo has little if any 
potential to ever develop into a normal human being. This is because, 
by circumventing the normal processes of gametogenesis and 
fertilization, nuclear cloning prevents the proper reprogramming of 
the clone's genome, which is a prerequisite for development of an 
embryo to a normal individual. It is unlikely that these biological 
barriers to normal development can be solved in the foreseeable 
future. Therefore, from a biologist's point of view, the cloned human 
embryo, used for the derivation of an embryonic stem cell and the 
subsequent therapy of a needy patient, has little if any potential to 
create a normal human life. 2) Embryonic stem cells developed from 
a cloned embryo are functionally indistinguishable from those that 
have been generated from embryos derived by in vitro fertilization 
(IVF). Both types of embryonic stem cells have an identical potential 
to serve as a source for therapeutically useful cells. 
It is crucial that the ongoing debate on the possible therapeutic 
application of SNCT is based on biological facts. The goal of this 
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