Human Cloning - Saskatchewan Elocution and Debate Association

Brave New World Page 4 of 5
Smithsonian, December 2001
have been recent reports of
human babies who have genetic
material from three adults, due
to a technique that uses healthy
mitochondria from a donor's egg
to enhance fertility.) So, though
Dolly resembled her DNA
donor, other sheep that Wilmut
and his colleagues have cloned
vary in appearance and
temperament from their DNA
donors as well as from other
clones developed from the same
DNA.
It is also important to note that
Dolly was born only after more
than 200 other clones were
spontaneously aborted or
stillborn. Attempts to clone
animals since have often
resulted in severe birth defects
— from dramatically increased
birth size to enlarged organs to
immune deficiencies. Going
back to the blueprint analogy,
Cornell professor and cloning
expert Jonathan Hill adds, "It
seems the cloned DNA is not
only a 'used' blueprint but one
that may have certain pages
stuck together, making some of
the details particularly hard to
read."
As a result of these and other
factors, many scientists — and
politicians — believe there
should be a ban on human
cloning. Others are wary that
such a ban might be too
restrictive, since some
techniques used in cloning are
also used in other promising
areas of science — including
applications of IVF technology
and stem cell research.
STEM CELL RESEARCH
Cloning and stem cell research
are connected in at least one
important way. Every one of the
trillions of cells in our bodies
(including our eggs and sperm,
which have but one set instead
of two) contain the same DNA.
The cells in your skin, for
example, contain the same gene
for producing insulin as those in
certain regions of your pancreas,
but only the latter actually make
the protein. Most of the genes in
our cells are inactive, leaving
only the relevant ones to do
their work. Though we know
little about how this occurs, we
do know that there is a period
early in development when the
cells have yet to begin the
processes of determination and
differentiation into blood,
muscle or any other kind of cell,
and all cells can still develop
into any cell in the adult. In
humans, this property — called
pluripotency — is lost by the
end of the second week after
fertilization.
Part of what made Wilmut's
success with Dolly so
extraordinary was that he seems
to have been able to revert an
adult sheep cell back to its
pluripotent state (though with
all of the unexplained
complications we've already
detailed). Other techniques are
being pursued for isolating adult
stem cells — cells that are only
partially differentiated — and
reverting them to a pluripotent
state, or nudging them to
develop in particular directions.
In the meantime, there is
another source of pluripotent
cells: the embryo itself.
Pluripotent cells from human
embryos are the embryonic stem
cells at the center of last
summer's debate.
Much of that continuing debate
centers on the fact that human
embryonic stem cells are
obtained, almost exclusively,
from embryos left over from
IVF. Though proponents of
research on them point out that
they would be destroyed
anyway, many opponents
believe that these embryos,
though comp0sed of just a few
dozen cells, are human lives,
and so should be saved.
The other reason that stem cells
have burst into the news has to
do with their exceptional
promise. Scientists have learned
to culture human embryonic
stem cells and allow them to
divide and multiply, while
preventing them from switching
on or off any of their genes. By
exposing these stem cells to
different molecular compounds,
they are trying to understand
how that switching process
works so that they can direct
this cell to become a neuron,
say, or that one to become a
blood cell. (These two
examples, in fact, are feats at
which they have already had
some measure of success.)
Eventually, some believe, we
may be able to control the
development of these
pluripotent cells so that we can
replace tissues damaged by
disease or accident. Nerve cells
damaged by Parkinson's or
spinal cord injury, for example,
or heart tissue of cardiac
patients, might ultimately be
replaced by tissue grown from
stem cells.
Some scientists see even the
potential to create custom-made
tissue by using stem cells that
are exact matches to a particular
person, thus obviating the
greatest problem in transplant
surgery — rejection of the
implant by the host's immune
system. "Therapeutic cloning,"
as this procedure has been
called, would involve inserting a