Human Cloning
Biotechnology: In Context, 2012
Introduction
A clone is an exact genetic copy. Bacteria and plants can be cloned naturally, but animal cloning is much
more difficult. When Dolly the sheep was cloned in 1997, however, it showed that animal cells could be
reprogrammed under certain experimental conditions, and achieving this in one mammalian species
suggested cloning would be possible in others, including humans.
Human cloning can refer to either therapeutic cloning or reproductive cloning. Both can, in theory at least,
be achieved using the same technology, nuclear transfer, used to create other clones in other species.
In therapeutic cloning, a human embryo is created from a somatic cell, such as a skin cell, and the cells in
this embryo are then used to make cells and tissues of various types, such as blood cells or neural cells,
that can be used to repair the body.
In human reproductive cloning, a process in which nuclear transfer would also be the first step, the goal
would be to create an embryo that could develop to term rather than being harvested for its cells. As of
2011, there have been no scientifically verifiable cases of human reproductive cloning.
Words to Know
Human embryonic stem cells
Human embryonic stem cells are just one source of stem cells. They are found, as the name
suggests, in the human embryo and have the capacity to develop into all the cells and tissues of
the human body.
Parthenogenesis
The development of a whole organism from an unfertilized egg, which is the main type of
reproduction in some organisms, including several insect species, such as some aphids, and
certain reptiles and fish.
Somatic cell nuclear transfer
The process by which animal cloning is achieved, involving transfer of a somatic, or body, cell to
an egg from which the nucleus has been removed. The transferred somatic cell begins to divide
and develop into an embryo.
Stem cell
A stem cell is a cell that is characterized by its potential to develop into many other cell types and
its ability to keep renewing itself through cell division.
Totipotent
Stem cells that have the ability to develop into any cell type and create a whole organism are said
to be totipotent. Plant cells and animal embryonic stem cells are totipotent.
Historical Background and Scientific Foundations
Since the nineteenth century, scientists have been intrigued by the question of whether cells are capable
of growing into a whole organism. Plant cells are totipotent, with an entire plant being generated easily
from a leaf or stem cutting. Moreover, the unfertilized eggs of some small invertebrates, and certain fish
and lizard species, are capable of parthenogenesis. In 1962 British developmental biologist John Gurdon
(1933–) achieved cloning in tadpoles when he inserted cells from the intestine of an adult frog into frog
eggs lacking a nucleus. The cloned tadpoles did not, however, survive to adulthood, but these early
attempts at nuclear transfer laid the groundwork for further work in animal cloning.
In 1995, after many attempts, researchers at the Roslin Institute near Edinburgh, Scotland, announced the
birth of two cloned sheep, Megan and Morag, from embryonic cells transferred into empty sheep eggs.
This was a landmark, showing that the differentiation of an embryo could be reversed. A natural next step
was to see if the clock could be similarly reversed in adult cells. Nuclear transfer was used again to clone
Dolly the sheep, born in 1996, from an udder cell.
Three sheep were involved in the creation of Dolly. The egg came from a Scottish Blackface with the
original nucleus removed. A Finn Dorset ewe donated a sample of udder cells, which were placed in a
glass dish and given enough nutrients to keep them alive, but not enough to let them grow and divide in
the usual way. This approach stopped the cells from developing and made them revert to a primitive stem
cell state. One of these cells was then inserted into the egg and a pulse of electric current was applied to it
to start off the development—making the egg behave as if it had been fertilized. The egg was then placed
into the womb of a third sheep who was Dolly’s “mother” in the sense of carrying, nurturing, and giving
birth to the developing fetus. However, Dolly did not have a mother, or a father, in the usual sense of the
word. Analysis of her DNA showed that her genetic blueprint was that of the udder cell of the Finn Dorset
sheep. Had she been conceived in the usual way, her genetic blueprint would have come half from her
mother (the egg) and half from her father (the sperm). Since Dolly, many other animals have been
cloned—mice, goats, rabbits, cows, pigs, dogs, cats, monkeys, and a gaur (a type of wild ox that is an
endangered species). There is no scientific reason why the nuclear transfer approach could not be used to
clone a human.
In 2004 Hwang Woo-Suk (1953–), of Seoul National University, South Korea, announced the cloning of a
number of human embryos but later admitted that the claim had been fabricated. Thus far, human cloning
has not been achieved, although many scientists believe it is sure to happen at some point in the future
unless prohibited by law or industry ethics agreements. Note that the clone is not an exact copy of the
somatic cell donor, because the empty egg has lost its nucleus, but it will still contain the original
mitochondria, which carry a small number of genes. These will also be present in the clone, as well as the
genes from the donor somatic cell.
In Context: Disputed Claims of Human Cloning
In 2001, a company called Advanced Cell Technology successfully cloned human embryonic cells that
were allowed to undergo several rounds of division. While not yet recognizable as an embryo, the
experiment demonstrated that the process was possible. With the realization that cloning was
achievable, public concern about the possibility that a human could be cloned grew.
The debate was further fueled by one group's highly disputed, and scientifically dubious, claim to have
produced a human clone. In May 1997, an international religious cult called the Raelians announced it
was creating a company called Clonaid to sponsor research in human cloning. By 2001 the company
claimed to have cloned a human embryo, a baby called Eve, allegedly born in 2002. Clonaid refused,
however, to allow genetic tests to prove its case. The company's CEO promised to deliver proof of the
successful clone in 2003, but produced only a photograph. Without any scientific proof, the vast majority
of reproductive scientists also dismissed the cult's claims to have produced other living clones.
Impacts and Issues
Human therapeutic cloning could play an important role in regenerative medicine by providing embryonic
stem cells for treatment that are derived from the patient’s own cells. For instance, patients requiring a
bone marrow transplant would no longer have to wait for a compatible donor. They could be treated with
their own bone marrow stem cells, derived from a nuclear transfer experiment. Other potential applications
of regenerative medicine include brain repair in stroke, Parkinson’s disease, and Alzheimer’s disease,
repair of the heart after a heart attack, and supply of insulin-producing cells to the pancreas to treat Type 1
Diabetes. Many of these treatments are still at the research stage, but some are already being used in
clinical trials to treat patients using stem cells from various sources. Regenerative medicine opens up the
possibility of renewing and repairing the human body as it ages and promises to be a viable alternative to
drug therapies.
However, there are ethical objections to human therapeutic cloning because it involves creating an embryo
solely for someone else’s use. It will never be implanted into a woman’s womb, so it can never have a
life of its own. Some people argue that an embryo is not a person until it has been implanted in the womb.
Others believe that life begins at conception, so an embryo of any age is a person. For these people,
therapeutic cloning is unacceptable, whatever benefit it brings, because it is against human dignity.
Additionally, animal cloning has also proved to be very inefficient, with 277 attempts needed to create
Dolly. There is no reason to think that human cloning would be any more successful, so a large supply of
donated human eggs would be required. When women donate eggs, it is usually as part of an in vitro
fertilization (IVF) program intended to create a baby. Egg donation is not a trivial process, because it
involves administration of powerful drugs and a surgical egg retrieval procedure, so there are some risks
to the woman. It may not, therefore, be practical or ethical to use human eggs for nuclear transfer until the
success rate of the process improves. This has led some scientists to propose the use of cow eggs
instead, and a few laboratories around the world have permission to research interspecies nuclear
transfer. The new procedure is controversial because it creates a chimeric or hybrid embryo with a mixture
of cow and human cells.
The second possible fate of a cloned human embryo, if one could be created, is to grow and develop into
a baby. Reproductive cloning has a number of potential applications. Bereaved parents could replace a
dead child or an infertile woman could use a cell from anywhere in her body to create a baby. Cloning
plants and animals has now been widely used to reproduce high value crops and valuable farm animals or
racehorses. Perhaps, if they had access to the technology, powerful businesspeople or politicians would
try to clone armies of obedient workers or disciplined soldiers. It is also possible that tissue preserved from
deceased celebrities could be used to clone new copies of them. Also concerning is the prospect of people
creating a clone that could be killed for its organs if they were in need of a transplant, which could be
considered a more extreme version of therapeutic cloning. The numerous possibilities offered by human
cloning mean it is important to have discussions about where the boundaries lie. Currently, human
reproductive cloning is outlawed in countries that have legislated cloning science, whereas research on
therapeutic cloning is allowed in some countries.
Besides the general ethical arguments over whether reproductive cloning is right or wrong, there are also
practical and safety issues to be considered. For instance, the embryo would need to be implanted in the
womb of a so-called surrogate mother. A woman would have to consent to have her womb used in this
way. Then there is the health of the clone itself to consider. Dolly the sheep suffered from arthritis and
excessive weight, although she did give birth to some normal lambs. Studies on other animal clones have
shown they are often much bigger than normal and have abnormally large organs, which leads to
breathing, circulation, and other medical problems.
Often it is said that cloning is wrong because it is “unnatural.” However, organ transplants and IVF were
thought unnatural when they were first introduced, and many of the same arguments, now being used
against cloning, were advanced. In 2011, a number of public surveys in the United States and United
Kingdom indicated that most (but not all) people accepted transplantation and assisted reproduction.
Further Readings
Books
Brown, Terry. Gene Cloning and DNA Analysis: An Introduction, 5th ed. Oxford, UK: Blackwell Science,
2006.
Caplan, Arthur and Glenn McGee, eds. The Human Cloning Debate. Berkeley: Berkeley Hills Books, 2006.
Harris, John. On Cloning. New York: Routledge, 2004.
Wilmut, Ian, and Roger Highfield. After Dolly: The Promise and Perils of Cloning. New York: W.W. Norton,
2007.
Web Sites
U.S. Department of Energy (DOE) Genomes Programs. “Cloning Fact Sheet.” genomics.energy.gov.
http://www.ornl.gov/sci/techresources/Human_Genome/elsi/cloning.shtml (accessed September 9, 2011).
Full Text: COPYRIGHT 2012 Gale, Cengage Learning.
Source Citation
Aldridge, Susan. "Human Cloning." Biotechnology: In Context. Ed. Brenda Wilmoth
Lerner and K. Lee Lerner. Detroit: Gale, 2012. In Context Series. Student
Resources in Context. Web. 12 Nov. 2013.
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