Programs: Science and Policy
AAAS Policy Brief: Human Cloning
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.
The Link to Stem Cell Research
Arguments Against Nuclear Transplantation Research
Arguments For Nuclear Transplantation Research
The States' Perspective
The International Perspective
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."
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
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.
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.
to view AAAS's position on human cloning.
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.
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.
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.
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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