Replacing Cells - Biotechnology and Your Health: Pharmaceutical Applications - page 111

orchestrated process of calling up particular sets of those instruc-
tions and manufacturing the proteins as instructed so that the
resulting specialized cells can perform particular functions. In very
simple terms, the control of the process is what makes a liver cell
perform liver functions instead of growing hair. This specialization
does not occur in a single step. Instead, it happens as a series of
discrete steps that the cells take as they commit to becoming a
particular kind of cell. This process of commitment to specializa-
tion is called differentiation . The embryo cell, and the cells produced
during the first few rounds of cell division, retain the ability to
become any type of cell in the body. As the cells of the embryo
go through more rounds of cell division, the cells become more
specialized and the kind of tissue or organ they can build appears to
become more limited (Figure 8.3).
U.S. Policy on Stem Cell Research
Few things have stirred more debate than the prospect of human cloning —producing
an exact genetic copy of a person from his or her cells. There is little or no support for
cloning to produce a child, because of both safety and ethical concerns. However, the
potential of embryonic stem cells and therapeutic human cloning to provide treatments
for a number of devastating and untreatable conditions, such as Parkinson's disease,
has received substantial support and media attention. Animal experiments suggest that
embryonic stem cells may be able to provide cells to treat Parkinson's disease, multi-
ple sclerosis, brain and spinal cord injury, diabetes, hearts damaged by heart attacks,
and many other conditions. Scientists have suggested that somatic nuclear transfer
(SNT) be used to generate embryonic stem cells to avoid the risk that the patient's
immune system will attack and destroy the transplanted cells.
In 2001, President George W. Bush developed a U.S. policy regarding work with
human ES cells. He proclaimed a ban on the use of federal funds for work on human
ES cell lines that were not generated before August 9, 2001. Federally funded
researchers may work on human ES cell lines created before that date. Research on
human ES cells is going on without these conditions in several other countries. Several
states, including California, have passed laws providing funding for work on human
ES cells within the state.