AAAS Policy Brief: Human Cloning
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The issue of human cloning has been the subject of much
public debate since the birth
of the cloned sheep Dolly was announced in 1997. The profound ethical
questions surrounding the prospect of the birth of a human clone have
received much scrutiny. In recent months, the debate has included the
topic of human
embryonic stem cell research, which scientists believe could benefit
from experimentation using the procedure pioneered by the scientists who
produced Dolly.
Nuclear Transplantation
The Link to Stem Cell Research
Legislative Debate
Arguments Against Nuclear Transplantation Research
Arguments For Nuclear Transplantation Research
The States' Perspective
The International Perspective
Nuclear Transplantation
This procedure is known as nuclear transplantation, or somatic
cell nuclear transfer (SCNT). It involves removing the nucleus, which
contains a cell's DNA, from an egg cell and transplanting the DNA from
an adult cell into the enucleated egg. Under certain conditions, the egg
then begins to replicate as though it were a fertilized embryo.
After the egg divides for several days, it produces embryonic
stem cells, which are primitive cells that can theoretically develop into
virtually any type of cells in the organism, from blood cells to skin
cells. Scientists believe that research on human stem cells could lead
to new cures for many diseases. The use of nuclear transplantation to
produce human stem cells is often referred to as "research cloning"
or "therapeutic cloning."
If this entity is implanted into a uterus, it has the potential
to develop into a full organism which would have the same DNA as the donor
of the adult cell. In other words, the organism would be a "clone."
This procedure is known as "reproductive cloning."
The Link to Stem Cell Research
Stem cell research and research cloning are closely linked.
Scientists in the private sector have conducted experiments on human embryonic
stem cells after extracting them from excess embryos left over from fertility
treatments. They hope one day to use these cells for treating diseases,
and one of the potential obstacles for such a procedure is rejection of
the implanted cells by the patient's immune system. Through nuclear transplantation,
stem cells could be created with the same genetic makeup as the patient,
which some scientists believe would reduce or eliminate the risk of immune
rejection.
Recently, various alternatives to nuclear transplantation
have been proposed, including:
- deriving stem cells from embryos that are already dead - some consider
this procedure to be ethically analogous to removal of organs from a
person who has recently died
- deriving stem cells by extracting blastomeres (cells formed in the
first stages of embryonic development, when the fertilized ovum is split)
from living embryos - this procedure is currently used to test IVF embryos
for genetic and chromosomal abnormalities, but long-term effects of
this extraction on a person's health are unknown
- altered nuclear transfer - this procedure alters the somatic cell
nucleus before transfer such that it would not have the developmental
potential of a human embryo
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for more information on these alternatives.
It is important to keep in mind that nuclear transplantation and its
alternatives are very recent developments - the science is still in its
early stages and there remains much to be learned. While nuclear transplantation
has been tested in animals with some success, such tests have not been
conducted for many of the alternatives to nuclear transplantation. Similarly,
ethical implications have been more thoroughly discussed in regards to
nuclear transplantation than its alternatives. Each method poses its own
set of ethical concerns.
Legislative Debate
There is widespread opposition in the U.S. to the birth
of a human clone (reproductive cloning). While a few groups argue that
cloning is a legitimate form of reproduction, opposition to these arguments
is nearly unanimous among scientists and policy-makers, due to both ethical
and safety concerns. To quote the National
Academies 2002 report on cloning, "Human reproductive cloning
should not now be practiced. It is dangerous and likely to fail."
However, both the U.S. as a whole and the U.S. Congress
in particular are heavily divided on the issue of research cloning. Some
in Congress support legislation criminalizing nuclear transplantation
in humans, whether for reproductive or research purposes, which is a position
supported by President Bush. Others in Congress have proposed legislation
that would criminalize only reproductive cloning while allowing research
cloning. Although various legislation
on this issue has been introduced in Congress from 2001 through the present,
no agreement has been reached.
Click here
to view AAAS's position on human cloning.
Arguments Against Nuclear Transplantation
Research
Proponents of a comprehensive ban
on nuclear transplantation for research and reproductive purposes raise
two main arguments. Religious conservatives argue that human embryos should
be afforded a moral status similar to human beings and should not be destroyed,
even in the course of conducting research. They also argue that permitting
nuclear transplantation would open the door to reproductive cloning, because
a ban only on implantation would be difficult to enforce. In this second
argument, conservatives are joined by a coalition of environmental, women's
health, and bioethics groups who are not unalterably opposed to nuclear
transplantation, but believe that it should not be permitted until strict
regulations are in place.
Arguments For Nuclear Transplantation
Research
Proponents of a ban solely on reproductive
cloning that would permit nuclear transplantation research, include a
coalition of science organizations, patient groups, and the biotechnology
industry. These groups argue that the moral status of a human embryo is
less than that of a full human being, and must be weighed against the
potential cures that could be produced by research using nuclear transplantation.
They contend that a ban on implantation on the product of nuclear transplantation
would be no more difficult to enforce than a ban on nuclear transplantation
itself. They argue further that criminalizing scientific research, which
has been done only very rarely in the past, would set a bad precedent.
The States' Perspective
In the United States, the absence of a national policy in
regards to cloning has resulted in states leading the way, pursuing policies
either for or against cloning. Opinions vary among the states. As of 2006,
fifteen states had laws dealing with human cloning. All either prohibit
reproductive cloning entirely or prohibit the use of government funding
for reproductive cloning. There is less agreement when it comes to research
cloning. Some ban it entirely and some prohibit the use of government
funding for it, but others allow it.
While the federal government has not addressed the overall issue of whether
cloning is allowed, it has addressed the funding of research via the Dickey
Amendment (H.R.
3010, Sec. 509) which prohibits the NIH from funding research utilizing
human embryos derived by cloning.
Please click here
for details.
The International Perspective
There is as little consensus among nations as there is among Congress
members when it comes to the issue of cloning. In fact, nations are so
divided that the United Nations abandoned efforts to create a worldwide
treaty on human cloning. Instead, in 2005 the U.N. adopted a resolution
aiming to provide guidance to countries attempting to arrive at a position
on cloning and stem cell research. Many nations, including the UK, China,
and South Africa, have explicitly prohibited reproductive cloning while
allowing research cloning. Fewer nations have explicitly prohibited research
cloning, which (as of 2006) is allowed in 10 countries.
Please click here
for details.
Updated June 6, 2007
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