research on animal cloning

Animal cloning

So Dolly was not the first clone, and she looked like any other sheep, so why did she cause so much excitement and concern? Because she was the first mammal to be cloned from an adult cell, rather than an embryo. This was a major scientific achievement, but also raised ethical concerns. Since 1996, when Dolly was born, other sheep have been cloned from adult cells, as have mice, rabbits, horses and donkeys, pigs, goats and cattle. In 2004 a mouse was cloned using a nucleus from an olfactory neuron, showing that the donor nucleus can come from a tissue of the body that does not normally divide.

How was Dolly produced?

Producing an animal clone from an adult cell is obviously much more complex and difficult than growing a plant from a cutting. So when scientists working at the Roslin Institute in Scotland produced Dolly, the only lamb born from 277 attempts, it was a major news story around the world. To produce Dolly, the scientists used the nucleus of an udder cell from a six-year-old Finn Dorset white sheep. The nucleus contains nearly all the cell's genes. They had to find a way to 'reprogram' the udder cells - to keep them alive but stop them growing – which they achieved by altering the growth medium (the ‘soup’ in which the cells were kept alive). Then they injected the cell into an unfertilised egg cell which had had its nucleus removed, and made the cells fuse by using electrical pulses. The unfertilised egg cell came from a Scottish Blackface ewe. When the scientists had managed to fuse the nucleus from the adult white sheep cell with the egg cell from the black-faced sheep, they needed to make sure that the resulting cell would develop into an embryo. They cultured it for six or seven days to see if it divided and  developed normally, before implanting it into a surrogate mother, another Scottish Blackface ewe. Dolly had a white face. From 277 cell fusions, 29 early embryos developed and were implanted into 13 surrogate mothers. But only one pregnancy went to full term, and the 6.6kg Finn Dorset lamb 6LLS (alias Dolly) was born after 148 days.

Why are scientists interested in cloning?

The main reason that the scientists at Roslin wanted to be able to clone sheep and other large animals was connected with their research aimed at producing medicines in the milk of such animals. Researchers have managed to transfer human genes that produce useful proteins into sheep and cows, so that they can produce, for instance, the blood clotting agent factor IX to treat haemophilia or alpha-1-antitrypsin to treat cystic fibrosis and other lung conditions. Cloned animals could also be developed that would produce human antibodies against infectious diseases and even cancers. ‘Foreign’ genes have been transplanted into zebra fish, which are widely used in laboratories, and embryos cloned from these fish express the foreign protein. If this technique can be applied to mammalian cells and the cells cultured to produce cloned animals, these could then breed conventionally to form flocks of genetically engineered animals all producing medicines in their milk. There are other medical and scientific reasons for the interest in cloning. It is already being used alongside genetic techniques in the  development of animal organs for transplant into humans (xenotransplantation). Combining such genetic techniques with cloning of pigs (achieved for the first time in March 2000) would lead to a reliable supply of suitable donor organs. The use of pig organs has been hampered by the presence of a sugar, alpha gal, on pig cells, but in 2002 scientists succeeded in knocking out the gene that makes it, and these ‘knockout’ pigs could be bred naturally. However, there are still worries about virus transmission. The study of animal clones and cloned cells could lead to greater understanding of the development of the embryo and of ageing and  age-related diseases. Cloned mice become obese, with related symptoms such as raised plasma insulin and leptin levels, though their offspring do not and are normal. Cloning could be used to create better animal models of diseases, which could in turn lead to further progress in understanding and treating those diseases. It could even enhance biodiversity by ensuring the continuation of rare breeds and endangered species.

What happened to Dolly?

Dolly, probably the most famous sheep in the world, lived a pampered existence at the Roslin Institute. She mated and produced normal offspring in the normal way, showing that such cloned animals can reproduce. Born on 5 July 1996, she was euthanased on 14 February 2003, aged six and a half. Sheep can live to age 11 or 12, but Dolly suffered from arthritis in a hind leg joint and from sheep pulmonary adenomatosis, a virus-induced lung tumour to which sheep raised indoors are prone. On 2 February 2003, Australia's first cloned sheep died unexpectedly at the age of two years and 10 months. The cause of death was unknown and the carcass was quickly cremated as it was decomposing. Dolly’s chromosomes were are a little shorter than those of other sheep, but in most other ways she was the same as any other sheep of her chronological age. However, her early ageing may reflect that she was raised from the nucleus of a 6-year old sheep. Study of her cells also revealed that the very small amount of DNA outside the nucleus, in the mitochondria of the cells, is all inherited from the donor egg cell, not from the donor nucleus like the rest of her DNA. So she is not a completely identical copy. This finding could be important for sex-linked diseases such as haemophilia, and certain neuromuscular, brain and kidney conditions that are passed on through the mother's side of the family only.

Improving the technology

Scientists are working on ways to improve the technology. For example, when two genetically identical cloned mice embryos are combined, the aggregate embryo is more likely to survive to birth. Improvements in the culture medium may also help.

Ethical concerns and regulation

Most of the ethical concerns about cloning relate to the possibility that it might be used to clone humans. There would be enormous technical difficulties. As the technology stands at present, it would have to involve women willing to donate perhaps hundreds of eggs, surrogate pregnancies with high rates of miscarriage and stillbirth, and the possibility of premature ageing and high cancer rates for any children so produced. However, in 2004 South Korean scientists announced that they had cloned 30 human embryos, grown them in the laboratory until they were a hollow ball of cells, and produced a line of stem cells from them. Further ethical discussion was raised in 2008 when scientists succeeded in cloning mice from tissue that had been frozen for 16 years. In the USA, President Clinton asked the National Bioethics Commission and Congress to examine the issues, and in the UK the House of Commons Science and Technology Committee, the Human Embryology and Fertilisation Authority and the Human Genetics Advisory Commission all consulted widely and advised that human cloning should be banned. The Council of Europe has banned human cloning: in fact most countries have banned the use of cloning to produce human babies (human reproductive cloning). However, there is one important medical aspect of cloning technology that could be applied to humans, which people may find less objectionable. This is therapeutic cloning (or cell nucleus replacement) for tissue engineering, in which tissues, rather than a baby, are created. In therapeutic cloning, single cells would be taken from a person and 'reprogrammed' to create stem cells, which have the potential to  develop into any type of cell in the body. When needed, the stem cells could be thawed and then induced to grow into particular types of cell such as heart, liver or brain cells that could be used in medical treatment. Reprogramming cells is likely to prove technically difficult. Therapeutic cloning research is already being conducted in animals, and stem cells have been grown by this method and transplanted back into the original donor animal. In humans, this technique would revolutionise cell and tissue transplantation as a method of treating diseases. However, it is a very new science and has raised ethical concerns. In the UK a group headed by the Chief Medical Officer, Professor Liam Donaldson, has recommended that research on early human embryos should be allowed. The Human Fertilisation and Embryology Act was amended in 2001 to allow the use of embryos for stem cell research and consequently the HFEA has the responsibility for regulating all embryonic stem cell research in the UK. There is a potential supply of early embryos as patients undergoing in-vitro fertilisation usually produce a surplus of fertilised eggs. As far as animal cloning is concerned, all cloning for research or medical purposes in the UK must be approved by the Home Office under the strict controls of the Animals (Scientific Procedures) Act 1986 . This safeguards animal welfare while allowing important scientific and medical research to go ahead.

Further information

The Roslin Institute has lots of information about the research that led to Dolly, and the scientific studies of Dolly, as well as links to many other sites that provide useful information on the scientific and ethical aspects of this research. The report of the Chief Medical Officer's Expert Advisory Group on Therapeutic Cloning: Stem cell research: medical progress with responsibility is available from the UK Department of Health , PO Box 777, London SE1 6XH. Further information on therapeutic cloning and stem cell research is available from the Medical Research Council . Interesting illustrated features on cloning have been published by Time , New Scientist . BBC News Online has a Q&A What is Cloning?   IMAGE © THE ROSLIN INSTITUTE

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Cloning Fact Sheet

The term cloning describes a number of different processes that can be used to produce genetically identical copies of a biological entity. The copied material, which has the same genetic makeup as the original, is referred to as a clone. Researchers have cloned a wide range of biological materials, including genes, cells, tissues and even entire organisms, such as a sheep.

Do clones ever occur naturally?

Yes. In nature, some plants and single-celled organisms, such as bacteria , produce genetically identical offspring through a process called asexual reproduction. In asexual reproduction, a new individual is generated from a copy of a single cell from the parent organism.

Natural clones, also known as identical twins, occur in humans and other mammals. These twins are produced when a fertilized egg splits, creating two or more embryos that carry almost identical DNA . Identical twins have nearly the same genetic makeup as each other, but they are genetically different from either parent.

What are the types of artificial cloning?

There are three different types of artificial cloning: gene cloning, reproductive cloning and therapeutic cloning.

Gene cloning produces copies of genes or segments of DNA. Reproductive cloning produces copies of whole animals. Therapeutic cloning produces embryonic stem cells for experiments aimed at creating tissues to replace injured or diseased tissues.

Gene cloning, also known as DNA cloning, is a very different process from reproductive and therapeutic cloning. Reproductive and therapeutic cloning share many of the same techniques, but are done for different purposes.

What sort of cloning research is going on at NHGRI?

Gene cloning is the most common type of cloning done by researchers at NHGRI. NHGRI researchers have not cloned any mammals and NHGRI does not clone humans.

How are genes cloned?

Researchers routinely use cloning techniques to make copies of genes that they wish to study. The procedure consists of inserting a gene from one organism, often referred to as "foreign DNA," into the genetic material of a carrier called a vector. Examples of vectors include bacteria, yeast cells, viruses or plasmids, which are small DNA circles carried by bacteria. After the gene is inserted, the vector is placed in laboratory conditions that prompt it to multiply, resulting in the gene being copied many times over.

How are animals cloned?

In reproductive cloning, researchers remove a mature somatic cell , such as a skin cell, from an animal that they wish to copy. They then transfer the DNA of the donor animal's somatic cell into an egg cell, or oocyte, that has had its own DNA-containing nucleus removed.

Researchers can add the DNA from the somatic cell to the empty egg in two different ways. In the first method, they remove the DNA-containing nucleus of the somatic cell with a needle and inject it into the empty egg. In the second approach, they use an electrical current to fuse the entire somatic cell with the empty egg.

In both processes, the egg is allowed to develop into an early-stage embryo in the test-tube and then is implanted into the womb of an adult female animal.

Ultimately, the adult female gives birth to an animal that has the same genetic make up as the animal that donated the somatic cell. This young animal is referred to as a clone. Reproductive cloning may require the use of a surrogate mother to allow development of the cloned embryo, as was the case for the most famous cloned organism, Dolly the sheep.

What animals have been cloned?

Over the last 50 years, scientists have conducted cloning experiments in a wide range of animals using a variety of techniques. In 1979, researchers produced the first genetically identical mice by splitting mouse embryos in the test tube and then implanting the resulting embryos into the wombs of adult female mice. Shortly after that, researchers produced the first genetically identical cows, sheep and chickens by transferring the nucleus of a cell taken from an early embryo into an egg that had been emptied of its nucleus.

It was not until 1996, however, that researchers succeeded in cloning the first mammal from a mature (somatic) cell taken from an adult animal. After 276 attempts, Scottish researchers finally produced Dolly, the lamb from the udder cell of a 6-year-old sheep. Two years later, researchers in Japan cloned eight calves from a single cow, but only four survived.

Besides cattle and sheep, other mammals that have been cloned from somatic cells include: cat, deer, dog, horse, mule, ox, rabbit and rat. In addition, a rhesus monkey has been cloned by embryo splitting.

Have humans been cloned?

Despite several highly publicized claims, human cloning still appears to be fiction. There currently is no solid scientific evidence that anyone has cloned human embryos.

In 1998, scientists in South Korea claimed to have successfully cloned a human embryo, but said the experiment was interrupted very early when the clone was just a group of four cells. In 2002, Clonaid, part of a religious group that believes humans were created by extraterrestrials, held a news conference to announce the birth of what it claimed to be the first cloned human, a girl named Eve. However, despite repeated requests by the research community and the news media, Clonaid never provided any evidence to confirm the existence of this clone or the other 12 human clones it purportedly created.

In 2004, a group led by Woo-Suk Hwang of Seoul National University in South Korea published a paper in the journal Science in which it claimed to have created a cloned human embryo in a test tube. However, an independent scientific committee later found no proof to support the claim and, in January 2006, Science announced that Hwang's paper had been retracted.

From a technical perspective, cloning humans and other primates is more difficult than in other mammals. One reason is that two proteins essential to cell division, known as spindle proteins, are located very close to the chromosomes in primate eggs. Consequently, removal of the egg's nucleus to make room for the donor nucleus also removes the spindle proteins, interfering with cell division. In other mammals, such as cats, rabbits and mice, the two spindle proteins are spread throughout the egg. So, removal of the egg's nucleus does not result in loss of spindle proteins. In addition, some dyes and the ultraviolet light used to remove the egg's nucleus can damage the primate cell and prevent it from growing.

Do cloned animals always look identical?

No. Clones do not always look identical. Although clones share the same genetic material, the environment also plays a big role in how an organism turns out.

For example, the first cat to be cloned, named Cc, is a female calico cat that looks very different from her mother. The explanation for the difference is that the color and pattern of the coats of cats cannot be attributed exclusively to genes. A biological phenomenon involving inactivation of the X chromosome (See sex chromosome ) in every cell of the female cat (which has two X chromosomes) determines which coat color genes are switched off and which are switched on. The distribution of X inactivation, which seems to occur randomly, determines the appearance of the cat's coat.

What are the potential applications of cloned animals?

Reproductive cloning may enable researchers to make copies of animals with the potential benefits for the fields of medicine and agriculture.

For instance, the same Scottish researchers who cloned Dolly have cloned other sheep that have been genetically modified to produce milk that contains a human protein essential for blood clotting. The hope is that someday this protein can be purified from the milk and given to humans whose blood does not clot properly. Another possible use of cloned animals is for testing new drugs and treatment strategies. The great advantage of using cloned animals for drug testing is that they are all genetically identical, which means their responses to the drugs should be uniform rather than variable as seen in animals with different genetic make-ups.

After consulting with many independent scientists and experts in cloning, the U.S. Food and Drug Administration (FDA) decided in January 2008 that meat and milk from cloned animals, such as cattle, pigs and goats, are as safe as those from non-cloned animals. The FDA action means that researchers are now free to using cloning methods to make copies of animals with desirable agricultural traits, such as high milk production or lean meat. However, because cloning is still very expensive, it will likely take many years until food products from cloned animals actually appear in supermarkets.

Another application is to create clones to build populations of endangered, or possibly even extinct, species of animals. In 2001, researchers produced the first clone of an endangered species: a type of Asian ox known as a guar. Sadly, the baby guar, which had developed inside a surrogate cow mother, died just a few days after its birth. In 2003, another endangered type of ox, called the Banteg, was successfully cloned. Soon after, three African wildcats were cloned using frozen embryos as a source of DNA. Although some experts think cloning can save many species that would otherwise disappear, others argue that cloning produces a population of genetically identical individuals that lack the genetic variability necessary for species survival.

Some people also have expressed interest in having their deceased pets cloned in the hope of getting a similar animal to replace the dead one. But as shown by Cc the cloned cat, a clone may not turn out exactly like the original pet whose DNA was used to make the clone.

What are the potential drawbacks of cloning animals?

Reproductive cloning is a very inefficient technique and most cloned animal embryos cannot develop into healthy individuals. For instance, Dolly was the only clone to be born live out of a total of 277 cloned embryos. This very low efficiency, combined with safety concerns, presents a serious obstacle to the application of reproductive cloning.

Researchers have observed some adverse health effects in sheep and other mammals that have been cloned. These include an increase in birth size and a variety of defects in vital organs, such as the liver, brain and heart. Other consequences include premature aging and problems with the immune system. Another potential problem centers on the relative age of the cloned cell's chromosomes. As cells go through their normal rounds of division, the tips of the chromosomes, called telomeres, shrink. Over time, the telomeres become so short that the cell can no longer divide and, consequently, the cell dies. This is part of the natural aging process that seems to happen in all cell types. As a consequence, clones created from a cell taken from an adult might have chromosomes that are already shorter than normal, which may condemn the clones' cells to a shorter life span. Indeed, Dolly, who was cloned from the cell of a 6-year-old sheep, had chromosomes that were shorter than those of other sheep her age. Dolly died when she was six years old, about half the average sheep's 12-year lifespan.

What is therapeutic cloning?

Therapeutic cloning involves creating a cloned embryo for the sole purpose of producing embryonic stem cells with the same DNA as the donor cell. These stem cells can be used in experiments aimed at understanding disease and developing new treatments for disease. To date, there is no evidence that human embryos have been produced for therapeutic cloning.

The richest source of embryonic stem cells is tissue formed during the first five days after the egg has started to divide. At this stage of development, called the blastocyst, the embryo consists of a cluster of about 100 cells that can become any cell type. Stem cells are harvested from cloned embryos at this stage of development, resulting in destruction of the embryo while it is still in the test tube.

What are the potential applications of therapeutic cloning?

Researchers hope to use embryonic stem cells, which have the unique ability to generate virtually all types of cells in an organism, to grow healthy tissues in the laboratory that can be used replace injured or diseased tissues. In addition, it may be possible to learn more about the molecular causes of disease by studying embryonic stem cell lines from cloned embryos derived from the cells of animals or humans with different diseases. Finally, differentiated tissues derived from ES cells are excellent tools to test new therapeutic drugs.

What are the potential drawbacks of therapeutic cloning?

Many researchers think it is worthwhile to explore the use of embryonic stem cells as a path for treating human diseases. However, some experts are concerned about the striking similarities between stem cells and cancer cells. Both cell types have the ability to proliferate indefinitely and some studies show that after 60 cycles of cell division, stem cells can accumulate mutations that could lead to cancer. Therefore, the relationship between stem cells and cancer cells needs to be more clearly understood if stem cells are to be used to treat human disease.

What are some of the ethical issues related to cloning?

Gene cloning is a carefully regulated technique that is largely accepted today and used routinely in many labs worldwide. However, both reproductive and therapeutic cloning raise important ethical issues, especially as related to the potential use of these techniques in humans.

Reproductive cloning would present the potential of creating a human that is genetically identical to another person who has previously existed or who still exists. This may conflict with long-standing religious and societal values about human dignity, possibly infringing upon principles of individual freedom, identity and autonomy. However, some argue that reproductive cloning could help sterile couples fulfill their dream of parenthood. Others see human cloning as a way to avoid passing on a deleterious gene that runs in the family without having to undergo embryo screening or embryo selection.

Therapeutic cloning, while offering the potential for treating humans suffering from disease or injury, would require the destruction of human embryos in the test tube. Consequently, opponents argue that using this technique to collect embryonic stem cells is wrong, regardless of whether such cells are used to benefit sick or injured people.

Last updated: August 15, 2020

Scientists Clone Two Black-Footed Ferrets From Frozen Tissues in Conservation Effort

The aim of cloning the animals is to increase the genetic diversity of the endangered species

Will Sullivan

Daily Correspondent

Researchers have cloned two black-footed ferrets from preserved tissue samples in an effort to conserve the creatures, the United States Fish and Wildlife Service announced last week. The animals are the second and third ferret clones in history—the first was born in December 2020 .

Black-footed ferrets are endangered, and scientists hope the new clones can increase the genetic diversity of the species. The limited genetic diversity of the current population makes the animals more susceptible to diseases and genetic abnormalities, decreases their fertility rates and makes it harder for them to adapt in the wild, hampering their recovery .

“Genetic diversity is critical for resilience to environmental change,” Megan Owen , vice president of conservation science at the San Diego Zoo Wildlife Alliance, which contributed to the cloning effort, tells the Washington Post ’s Dino Grandoni. “It’s basically the raw material of adaptive evolution.”

The two new clones, named Noreen and Antonia, are healthy, and they have been reaching their expected developmental and behavioral milestones. Noreen was born at the National Black-footed Ferret Conservation Center in Colorado, while Antonia was born at the Smithsonian’s National Zoo & Conservation Biology Institute.

One of three ferret species, black-footed ferrets are native to North America and have lived on the continent for at least 100,000 years. Long and skinny, with light fur everywhere except for their black face masks, feet and tail tips, the mammals are nocturnal and mostly live underground.

An estimated 500,000 to 1 million black-footed ferrets lived during the late 1800s, and they historically roamed 12 states, northern Mexico and southern Canada. But in the 20th century, their numbers declined dramatically as farmers eradicated prairie dogs, which make up most of a black-footed ferret’s diet. Diseases including canine distemper and a form of plague wiped out ferrets and prairie dogs alike.

Researchers thought the last black-footed ferret might have died in 1979. But in 1981, a ranch dog brought a dead ferret home , leading to the discovery of a small population of the species near the town of Meeteetse, Wyoming.

In the following years, officials captured 24 ferrets and started a breeding program. Since then, they have grown the species’ population and introduced ferrets back into the wild at 34 sites across eight states, Canada and Mexico. The Fish and Wildlife Service estimates several hundred black-footed ferrets currently live in the wild.

While this effort preserved the species, it also set up a problem: All living black-footed ferrets are descended from only seven of the wild-caught animals, severely limiting their genetic diversity.

But the three cloned ferrets come from frozen tissue samples collected in 1988 from a ferret called Willa, which had been stored at the San Diego Zoo Wildlife Alliance’s Frozen Zoo .

Willa never reproduced, so her genes are not part of the captive black-footed ferret gene pool. Her samples contain three times as many unique genetic variations than the average in the current population, according to the Fish and Wildlife Service.

To clone the ferrets, researchers injected a cell from Willa into a domesticated ferret egg, per the Washington Post .

The Fish and Wildlife Service announced the birth of the first clone , Elizabeth Ann, in 2021. She lives at the National Black-footed Ferret Conservation Center and is healthy, but she has been unable to give birth.

Elizabeth Ann has a condition called hydrometra, where fluid fills the uterus. One of her uterine horns, where the fallopian tubes open into the uterus, did not fully develop. Since this condition is not unusual in black-footed ferrets, researchers don’t think it’s related to the cloning, per the Fish and Wildlife Service.

Once the two newborn ferrets reach maturity later this year, researchers will try to get them to have babies to pass on their genetic diversity.

Some of the ferret cloning project’s collaborators are also working to freeze tissue samples from every endangered species in the U.S., in case they can help combat extinction of these species in the future, reports Scientific American ’s Cari Shane.

The cloning research doesn’t replace the need for recovering ferrets in the wild, and the Fish and Wildlife Service is continuing to work on reintroducing animals, monitoring ones currently living in the wild and preserving their habitats.

“Some people think if you have [species] in a freezer, you don’t need them in the wild,” Seth Willey, a Fish and Wildlife Service deputy assistant regional director, tells Scientific American . “That’s just not true… We can’t lose what we have in the wild. But if we do, it’s good to have an insurance policy.”

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Will Sullivan | | READ MORE

Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next .

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• Review Article
• Published: 01 December 2000

Mammalian cloning: advances and limitations

• Davor Solter 1  

Nature Reviews Genetics volume  1 ,  pages 199–207 ( 2000 ) Cite this article

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For many years, researchers cloning mammals experienced little success, but recent advances have led to the successful cloning of several mammalian species. However, cloning by the transfer of nuclei from adult cells is still a hit-and-miss procedure, and it is not clear what technical and biological factors underlie this. Our understanding of the molecular basis of reprogramming remains extremely limited and affects experimental approaches towards increasing the success rate of cloning. Given the future practical benefits that cloning can offer, the time has come to address what should be done to resolve this problem.

Several mammalian species have been cloned by transferring nuclei from various adult somatic cells into enucleated oocytes.

The cloning procedure is still inefficient, and only one in a hundred of manipulated oocytes develop to adulthood.

Reasons for the low efficiency of cloning are largely unknown and are probably both technical and biological.

The incomplete or incorrect reprogramming of the donor nuclear genome — its inability to completely adapt and function in the new environment — is the most significant factor contributing to low cloning efficiency.

The cloning of large farm animals from genetically manipulated donor nuclei will have significant practical benefits.

The cloning of humans is prohibited because of safety reasons at present. However, therapeutic cloning and the production of individualized human embryonic stem cells for use in cell- and tissue-replacement therapies may have great importance in human medicine.

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Acknowledgements

I would like to thank Professor Ryuzo Yanagimachi from the University of Hawaii for kindly giving permission to reproduce Figures 3 and 4 .

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In his Image: The Cloning of a Man

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ENCYCLOPEDIA OF LIFE SCIENCES

Nuclear transfer from established cell lines

Imprinting in mammals

Cleavage and gastrulation in mouse embryos

Sperm-egg binding in mammals

Cloning efficiency is calculated from the percentage of manipulated embryos that develops to adulthood, and reflects how successful or not a cloning experiment has been.

The use of nuclear transfer to produce individually tailored human embryonic stem cells for tissue- and cell-replacement therapies.

An isolated donor nucleus, together with its envelope of cytoplasm and plasma membrane.

Enucleated oocyte or embryo (zygote) that is used as a nuclear recipient.

The structure that is extruded from the oocyte during meiosis, which contains one haploid set of chromosomes.

Animals that are genetically engineered to produce proteins or macromolecules that are of use in human medicine.

The division of the cytoplasm of a parent cell into daughter cells after nuclear division.

This occurs when the binding of sperm to the egg cell membrane triggers a series of responses in the oocyte that prepare the oocyte for fertilization and block the entry of more sperm.

A series of repetitive oscillations in calcium concentration that move across the egg cytoplasm following sperm entry, which are essential for egg activation.

The presence of more than one type of mitochondrial DNA within the same cell.

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Animal Cloning

In 2001, when it became apparent that animal cloning may become a commercial venture to help improve the quality of herds, FDA requested livestock producers and researchers to keep food from animal clones or their offspring out of the food supply. Since then, FDA has conducted an intensive evaluation that included examining the safety of food from these animals and the risk to animal health.

Based on a final risk assessment, a report written by FDA scientists and issued in January 2008, FDA has concluded that meat and milk from cow, pig, and goat clones and the offspring of any animal clones are as safe as food we eat every day.

What is FDA Doing?

• Animal Cloning: A Risk Assessment (PDF - 22.3MB) Persons using assistive technology may not be able to fully access information in the Risk Assessment. For assistance, please call 240-402-7002.
• Risk Management Plan
• CVM GFI #179 Use of Animal Clones and Clone Progeny for Human Food/Animal Feed
• FDA's Response to Public Comment on the Animal Cloning Risk Assessment, Risk Management Plan, and Guidance for Industry
• CVM Memorandum I - Draft 5/21/03 Conference Call on Prenatal Care for Animal Clones and their Dams Summary
• CVM Memorandum II - ViaGen Industry Meetings

Consumer Health Information

• Myths about Cloning Responses to the questions provided in this document represent FDA's view in light of the conclusions and recommendations outlined in the Animal Cloning Risk Assessment, Risk Management Plan, and Guidance for Industry #179.
• A Primer on Cloning and Its Use in Livestock Operations Responses to the questions provided in this document represent FDA's view in light of the conclusions and recommendations outlined in the Animal Cloning Risk Assessment, Risk Management Plan, and Guidance for Industry #179.

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• Biotechnology Products at CVM: Animals and Animal Food
• University of Maryland AgNIC Agricultural Biotechnology Gateway
• Animal Biotechnology: Science Based Concerns
• Glossary of Biotechnology for Food and Agriculture United Nations, Food and Agriculture Organization
• 21 CFR Part 511--New Animal Drugs for Investigational Use
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ENCYCLOPEDIC ENTRY

Cloning is a technique scientists use to create exact genetic replicas of genes, cells, or animals.

Biology, Genetics, Health, Chemistry

Cloned Beagles

Two Beagle puppies successfully cloned in Seoul, South Korea. These two dogs were cloned by a biopharmaceutical company that specializes in stem cell based therapeutics.

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Cloning is a technique scientists use to make exact genetic copies of living things. Genes , cells, tissues, and even whole animals can all be cloned .

Some clones already exist in nature. Single-celled organisms like bacteria make exact copies of themselves each time they reproduce. In humans, identical twins are similar to clones . They share almost the exact same genes . Identical twins are created when a fertilized egg splits in two.

Scientists also make clones in the lab. They often clone genes in order to study and better understand them. To clone a gene , researchers take DNA from a living creature and insert it into a carrier like bacteria or yeast. Every time that carrier reproduces, a new copy of the gene is made.

Animals are cloned in one of two ways. The first is called embryo twinning. Scientists first split an embryo in half. Those two halves are then placed in a mother’s uterus. Each part of the embryo develops into a unique animal, and the two animals share the same genes . The second method is called somatic cell nuclear transfer. Somatic cells are all the cells that make up an organism, but that are not sperm or egg cells. Sperm and egg cells contain only one set of chromosomes , and when they join during fertilization, the mother’s chromosomes merge with the father’s. Somatic cells , on the other hand, already contain two full sets of chromosomes . To make a clone , scientists transfer the DNA from an animal’s somatic cell into an egg cell that has had its nucleus and DNA removed. The egg develops into an embryo that contains the same genes as the cell donor. Then the embryo is implanted into an adult female’s uterus to grow.

In 1996, Scottish scientists cloned the first animal, a sheep they named Dolly. She was cloned using an udder cell taken from an adult sheep. Since then, scientists have cloned cows, cats, deer, horses, and rabbits. They still have not cloned a human, though. In part, this is because it is difficult to produce a viable clone . In each attempt, there can be genetic mistakes that prevent the clone from surviving. It took scientists 276 attempts to get Dolly right. There are also ethical concerns about cloning a human being.

Researchers can use clones in many ways. An embryo made by cloning can be turned into a stem cell factory. Stem cells are an early form of cells that can grow into many different types of cells and tissues. Scientists can turn them into nerve cells to fix a damaged spinal cord or insulin-making cells to treat diabetes.

The cloning of animals has been used in a number of different applications. Animals have been cloned to have gene mutations that help scientists study diseases that develop in the animals. Livestock like cows and pigs have been cloned to produce more milk or meat. Clones can even “resurrect” a beloved pet that has died. In 2001, a cat named CC was the first pet to be created through cloning. Cloning might one day bring back extinct species like the woolly mammoth or giant panda.

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Animal Cloning ( See Animal Ethics; Animal Research; Cloning)

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Cloning in the animal world is achieved naturally in several ways. Asexual reproduction is when an organism creates a copy of itself without any contribution of genetic material from another individual. It is the most elementary form of (plant and) animal cloning and happens in nature through fragmentation (a new organism grows from a fragment of the progenitor), gemmulation (aggregates of cells mostly archaeocytes become isolated), and parthenogenesis (an unfertilized egg develops into a new individual). Although not involving genetic material from a second source, parthenogenesis can be considered sexual reproduction because it involves gametes.

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ten Have, H., Patrão Neves, M. (2021). Animal Cloning ( See Animal Ethics; Animal Research; Cloning). In: Dictionary of Global Bioethics. Springer, Cham. https://doi.org/10.1007/978-3-030-54161-3_53

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Research on animal cloning technologies and their implications in medical ethics: an update

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• 1 Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
• PMID: 11143888

Reproduction by cloning has been achieved by transfer into enucleated oocytes of nuclei from embryonic cells and more recently from cells of adult animals. The efficiency at which embryos produced by such nuclear transfers will develop into healthy newborns is very low but has allowed to produce some cloned bovines, bovines and mice. Since the first report of sheep cloning from an adult cell in 1997, the potential applications of reproductive cloning in human medicine have been envisaged amidst a flurry of moral debates. Although the technology is still far from being ready for any human use, it has been condemned from the outset. It has also led to irrational fantasies and fears mainly based on the misconception that genetic identity means identical twin personalities. Scientific research is ongoing on refining the cloning technology for applications in the production of genetically homogeneous farm animals with useful nutritional or therapeutic genetic traits. A new area of research is non-reproductive therapeutic cloning for the purpose of producing autologous embryonic cells and tissues for transplantation.

• Cloning, Organism*
• Ethics, Medical*
• Hematopoietic Stem Cell Transplantation
• Research / organization & administration*

Animal and Pet Cloning Opinion Polls

Americans very consistently oppose animal cloning in general. They specifically disapprove of pet cloning, and the use of cloning to reestablish endangered, or revive extinct, species.

The cloning and possible genetic modification of animals has been polled regularly since the announcement of the first cloned sheep in 1997. Almost immediately, applications and extensions of the technique were discussed, notably to standardize livestock, rescue endangered species and even to revive extinct species. It is notable that over more than 20 years, these proposed applications have never achieved general public acceptance.

Lou Hawthorne , an eccentric entrepreneur financed by John Sperling , tried to establish a pet cloning industry in the early 2000s, but abandoned the attempt when he (finally) realized that it was impossible without “a huge amount of suffering .” Nevertheless, the disgraced Korean stem-cell scientist Hwang Woo-Suk continues to sell cloned dogs for high prices, and occasionally derives headlines by selling to celebrities , including Barbra Streisand. In 2018, a Chinese company also entered the dog cloning market. Hwang  claims that he will revive mammoths by cloning; others, including Harvard’s George Church, aim to do the same by genetically editing an elephant.

Animals are routinely used in laboratories, and increasingly genetically modified for research purposes and perhaps for xenotransplantation. There is little if any polling on these topics, though medical applications of technology are generally less unpopular than recreational ones.

Poll Summary

Verbatim text of the questions, and complete survey reports, can generally be found by clicking on the links in the ‘Poll’ column; missing data is indicated by a dash. A few notes on phrasing and the very limited demographic data available follow the table.

The 2002–2022  Gallup polls, and the 1997 CNN/Time poll, asked whether animal cloning was "morally acceptable" or "morally wrong," as did the 2013 Angus Reid survey of Canada, the US and the UK. The 2001 Time/CNN poll asked if it was "a good idea or a bad idea." The 2002 Genetics and Public Policy Center ( GPPC ) poll asked for approval/disapproval of "scientists working on ways to clone animals."  

The January 2013 YouGov poll also asked about cloning Neanderthals, with or without a human surrogate, opposed 17–63 and 15–66, respectively. The January 2014 YouGov  survey asked about "woolly mammoths and other extinct species" and distinguished between strong and "somewhat" approval and disapproval (8% strongly approved, 34% strongly disapproved).

The April/May 2018  Pew poll includes an assessment of the science knowledge of respondents (24% high, 49% medium, 26% low) based on answers to nine factual questions, applied as part of a demographic analysis: “Men, those with high science knowledge and those low in religiosity are more inclined to see these varied uses of animal biotechnology as appropriate.” The main reasons (respondents were asked to name one) for objecting to specific proposals varied, frequently including risk of unintended consequences, animal welfare, “messing with” nature or God's plan, and being a waste of time and resources.

Very little other demographic data is available, and none recent. According to the 2001 Gallup and ABC polls, people with postgraduate education and those earning above $75,000 were more inclined to favor animal cloning. Religious people tended to be more opposed than the non-religious. There was also a substantial gender gap, with women strongly opposed to animal cloning (25–71% in the ABC poll, 74% opposed in the Gallup), and men almost evenly split.

The February 2004 Opinion Research Corporation ( ORC ) poll summary was prepared for the American Anti-Vivisection Society, and contains fairly detailed demographic breakdowns (opposition varied from 73% to 88%). It was the first and perhaps only only available poll that specifically addresses the issue of genetically modified (as distinguished from cloned) pets, and shows that they even more unpopular, with 84% opposing and only 12% approving of them.

Updated 4/18/2022

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The Pros and Cons of Animal Cloning

In 1996, a pair of scientists at the Roslin Institute at the University of Edinburgh embarked on an audacious venture. Taking the somatic cell from a 6-year-old Finn-Dorset ewe, biologists Dr. Keith Campbell and Sir Ian Wilmut inserted it in the ovum harvested from another sheep. After 276 attempts, an embryo was successfully seeded, then placed inside a third female sheep, where it underwent the gestation period typical of any normal pregnancy. 

On July 5, 1996, scientists’ bold undertaking became a roaring success when “ Dolly the Sheep ,” the first successfully cloned mammal, was born. 

Called the “ world’s most famous sheep ,” Dolly lived with her human creators at the Roslin Institute. Bred with a Welsh Mountain Ram, Dolly would produce six lambs before finally being euthanized at 6.5 years old due to progressive lung disease and severe arthritis. Dolly’s taxidermied remains are now on display at the National Museum of Scotland . 

Fast forward twenty-five years. Not wanting to be outdone by NASA’s successful landing of the Perseverance Rover on Mars , on February 18, 2021, officials with the U.S. Fish and Wildlife Service announced they had successfully cloned the first U.S. endangered species, a black-footed ferret named Elizabeth Ann. 

Looking at the photos released by Fish and Wildlife , with her adorable black eye markings resembling a robber’s mask, I had to fight the sudden urge to don a loincloth and fight an evil wizard army with Elizabeth Ann as my ever loyal side-kick, à la Beastmaster-style. However, there is one eerie difference between Elizabeth Ann the ferret and Dolly the Sheep.

Unlike Dolly, who technically had three living “mothers,” Elizabeth Ann was created using extracted cells from a black-footed ferret that had died 33 years prior. 

Born December 10, 2020, Elizabeth Ann is a genetic copy of a ferret named Willa, who died in 1988. At the time of her death, DNA technology was just in its infancy. Yet, astute (or mad) scientists froze the endangered ferret’s body, where it lay in cryogenic impassiveness, waiting until the day Willa could be “reborn.” 

Those who are already a bit squeamish with the 18 different mammal species geneticists have cloned in the past 20 years – including Mice, Pigs, Cattle, Cats, Rats, Mules, Horses, Dogs, Wolf, Water Buffalo, Goats, Camel, and even monkeys – scientist’s necromancy with Elizabeth Ann the ferret is likely pretty alarming. 

In hopes of gaining a better understanding of what feels like machiavellian-science, The Debrief takes a look at some of the pros and cons of animal cloning. 

The Pros and Cons of Animal Cloning 

It’s important to note up-front, the process of reproducing by sharing virtually identical DNA sequences does occur naturally. Living in clonal colonies, plants, fungi, and single-celled organisms, such as bacteria, have been reproducing asexually for hundreds of millions of years. 

Contrary to how it may look, recent research published in the journal of Nature Genetics shows that monozygotic or “identical” twins are not clones. After sequencing DNA from 387 pairs of identical twins, scientists found that mutations during early gestation create genetic differences in identical twins. On average, identical twins have 5.2 early genetic differences between each other. 

To examine some of the pros and cons of animal cloning, the term “cloning” here doesn’t refer to natural asexual reproduction or colloquialism. Instead, “cloning” refers to the method of artificial replication of identical cells, or DNA fragments, used to create a life that would otherwise reproduce sexually. 

Maintaining Ecological Balance and Saving Endangered Species 

Two decades ago, Yellowstone National Park was in a state of ecological crisis. 

Expansion of agriculture, the decimation of the American bison population, and government predator control programs had all but wiped out the Grey Wolf in the continental United States. With the apex predator on the brink of extinction, deer and elk populations dramatically increased, resulting in overgrazing. With deer and elk gobbling up vegetation important to soil and riverbank structure with impunity, the landscape became highly vulnerable to erosion. 

Recognizing the national park’s ecosystem’s elasticity was on the brink of collapse, in 1995, conservationists reintroduced the grey wolf   to Yellowstone, and suddenly everything changed. 

As a top predator, conservationists discovered wolves were one of the significant linchpins holding together the balance between predator and prey in Yellowstone’s ecosystem. Removal of the wolves had disrupted the food chain causing something called a  trophic cascade . 

Without facing the threat of a natural predator, deer and elk populations had multiplied to the point where they were consuming more foliage than the habitat could sustain. Consequently, the reintroduction of grey wolves to Yellowstone reduced the population numbers and changed their preys’ behavior. 

Deer and elk began avoiding the valleys and gorges at Yellowstone, where the wolves could easily hunt them. In turn, thanks to the revived food source of vegetation, these areas began to flourish with species such as birds, beavers, mice, foxes, and bears. The thriving plant life along the riverbanks caused erosion to decrease significantly.

Lessons learned from Yellowstone were that even the loss of just one species could have a cascading and catastrophic effect on an entire habitat and the environment. 

Given the devastating positive or negative effect just one species can have, consider for some, cloning is very literally the only way we might be able to save them from extinction. Take, for example, the white rhinoceros.

The world’s  last known male white rhinoceros named Sudan died  in Kenya in March of 2018. The only two confirmed white rhinos left are two females, Fau, 18, and Najin, 29, living in captivity in Kenya’s Ol Pejeta Conservancy. 

Without a male rhino to mate with, when Fau and Najin finally pass away, their entire species die with them. In hopes of preventing this demise, researchers have successfully taken frozen sperm extracted from two male rhinos after their deaths and inseminated it into eggs harvested from Fatu and Najin. As of 2020, three white rhino embryos have been generated, kept frozen until they can be placed in a surrogate female. 

As was demonstrated in the case of Dolly, cloned animals can still reproduce naturally to produce offspring. So the goal of cloning high-risk endangered species serves as an intervention. The end goal of cloning high-risk endangered species like the white rhino is to see the animals thrive and sustain themselves naturally and not be kept alive by human life-support. 

As is the case with Elizabeth Ann, cloning an endangered species could allow the animals to be reintroduced into a habitat to offset potential damage caused by their demise. With some critically endangered animals like the white rhino, cloning is simply the only method of saving species from complete extinction. 

So when it comes to the pros and cons of animal cloning, from the perspective of rescuing an entire species from extinction, it’s hard to make a case that animal cloning is a bad thing. 

Now, Elizabeth Ann’s DNA came from an animal that had been dead for over three decades, so her cloning might seem understandably creepy. However, though endangered, the black-footed ferret does indeed exist in limited populations in the wild. This brings us to the next question when examining the pros and cons of animal cloning. 

Could we resurrect a species that was already extinct, and if so, what could happen? 

Cloning Already Extinct Animals 

When it comes to the pros and cons of animal cloning, anyone who’s watched the movie franchise Jurassic Park is intimately familiar with the potential negative outcome of cloning extinct species. 

So what would happen if scientists cloned an animal that had long been extinct, like the saber-toothed tiger, woolly mammoth, or as is the case in Jurassic Park , a Velociraptor or Tyrannosaurus Rex? 

Fortunately for anyone who’s seen the habitual outcome in the movies (or unfortunately, if your thinking happens to align with the wealthy eccentric fictional character, John Hammond), resurrecting long-extinct dinosaurs is impossible. “The limit of DNA survival, which we’d need for de-extinction, is probably around one million years or less. Dinosaurs had been gone for a very long time by then,” said  Dr. Beth Shapiro, an expert in ancient DNA and biologist at the University of California. 

Even though the outcome always ends in tragedy, at least in the movies, one can’t help but feel a little let down by the news that we’ll never get a chance to see Earth’s ancient reptile rulers up close. 

Nevertheless, with dinosaurs off the table, there are still many species that have gone extinct we might be able to clone. There happens to be an entire scientific discipline called “ resurrection biology ” that examines doing just that. 

If you have not previously heard of resurrection biology, which sounds more like sorcery than science, you’re likely equally unfamiliar with the fact that scientists have already reanimated a species that had gone extinct. Albeit very briefly. 

In 2000, the Pyrenean ibex, a goat native to the Pyrenees , was declared extinct. Given that by 1913, ecologists already knew the species population had been reduced to less than 100, its loss has been called  a significant “EU conservation failure.” 

Yet, using skin cells from the last known ibex, which had died in late 1999, scientists were able to successfully make cloned embryos by inserting the ibex’s DNA into domestic goat eggs emptied of their original genetic material. 

The cloned embryos were then implanted into another subspecies of Spanish ibex or goat-ibex hybrids. Of 208 implanted embryos, seven goats became pregnant, with just one making it to term. On July 30, 2003, the  first-ever cloned extinct species  was born. 

Unfortunately, the Pyrenean ibex’s revival in the animal kingdom only lasted a few minutes. The newborn ibex had been born with an extra lobe in its left lung, causing the kid to succumb to respiratory distress syndrome and die six minutes after it was born. So far, researchers have not successfully cloned the Pyrenean ibex, and the mountain goat remains extinct. 

The difficulty in cloning a species is hardly limited to the Pyrenean ibex. With current technology, the act of shuffling DNA from one cell to another, causing developmental irregularities and abnormalities, is prevalent. 

Even when cells can be extracted and a cloned embryo successfully cultivated, scientists have to overcome another huge obstacle when working with an extinct species. There aren’t any appropriate surrogate mothers. 

Underscoring the difficulties in resurrecting an extinct species, consider with the Pyrenean ibex, researchers had the benefit of beginning their attempts almost immediately after the last goat died. Attempting to clone a species that has been gone for tens-to-hundreds-of-thousands of years is exceedingly more difficult. 

In fact, rather than using the process of somatic cell nuclear transfer – how Dolly the Sheep and Elizabeth Ann were created – to attempt the resurrection of an extinct species, scientists must engage in a process in which DNA is inserted, deleted, modified, or replaced in the genome of an organism. This technique is called genome editing or genome engineering. 

Due to  controversies surrounding the topic  and an often contentious public view , many are probably familiar with the term describing an organism’s successful genetic editing for increased food yield –  GMO (genetically modified organism) . 

To revive an animal long wiped out, resurrection biologists have to use cells from a closely related species and then modify those cells so that a living species produce offspring of an extinct species. A species that is at the forefront of de-extinction science right now is the  woolly mammoth . 

Disappearing roughly 3,700 years ago, scientists have well preserved soft tissue remains and DNA from woolly mammoths. Unfortunately, even the  most intact mammoth samples lack enough DNA to guide the production of an embryo. To overcome this, scientists have been examining using new molecular tools to edit the genomes of elephants to alter their DNA sequences to mammoth DNA. If successful, the result wouldn’t be a woolly mammoth clone, but rather a hybrid that would be mostly elephant, and a little bit mammoth. 

“If you mean 100-percent mammoth, with all mammoth genes and behaviors, that will never happen,” says Dr. Shapiro on the likelihood of ever fully cloning a woolly mammoth. 

If an extinct species can never really be restored, is there any reason for de-extinction outside of novelty? 

A June 2013 editorial by  Scientific American  criticized efforts to reanimate lost species on the basis the idea misses the mark when it comes to conservation. Editors argued that with “limited intellectual bandwidth and financial resources,” the attention-grabbing de-extinction topic diverts attention from the current biodiversity crisis. 

“A program to restore extinct species poses a risk of selling the public on a false promise that technology alone can solve our ongoing environmental woes—an implicit assurance that if a species goes away, we can snap our fingers and bring it back.” 

As far as pros and cons of animal cloning, the Scientific American editors said they stood behind efforts to prevent extinction, highlighting the black-footed ferret and white rhino as examples. 

Responding to the criticism raised by Scientific American, professor of genetics at Harvard Medical School and Director of the National Institutes of Health Center of Excellence in Genomic Science at Harvard, Dr. George Church, clapped back, suggesting the authors were the ones missing the point. 

For Dr. Church, it goes back to the grey wolves and Yellowstone National Park and the evidence of how impactful one “keystone” species can be, not just to one habitat but the entire world’s ecosystem. 

Thousands of years ago, the ice-covered tundras of Russia and Canada was home to the woolly mammoth. During that time, the area was home to a rich grass-and-ice-based ecosystems. Today, those tundras are melting, and according to Dr. Church, if this continues, it could release more greenhouse gas “than all the world’s forest would if they were burned to the ground.” 

A few genetic modifications to the modern elephant’s DNA could create a hybrid animal functionally similar to the mammoth. By reintroducing woolly mammoth hybrids to the tundras, the animals could single-handedly stave off an environmental crisis.

In an  essay published in Scientific American , Church outlines three significant ways mammoth hybrids would restore balance to the world’s coldest regions. 

• Eating dead grass, enabling the sun to reach spring grass, whose deep roots prevent erosion. 
• Increasing reflected light by felling trees, which absorb sunlight. 
• Punching through insulating snow so that freezing air penetrates the soil. 

Dr. Church provides a compelling case for why cloning for de-extinction is far from a novelty. As grey wolves demonstrated, the woolly mammoth’s return could have a significant positive impact on our planet’s ecology. However, objectively it’s essential to remember this is entirely uncharted territory for humanity, with considerable unknowns. 

Reintroducing a species that has been extinct for thousands of years could have the exact opposite effect as the grey wolf. An extinct species could easily be viewed as an invasive species by its former habitat. Instead of restoring balance, it could throw-off an ecosystem in ways we didn’t foresee. 

Given the ongoing and over a year-long struggle the world has endured with the COVID-19 pandemic, it’s also important to consider that reintroducing extinct animals could end up creating new opportunities for bacteria and viruses to develop. Even if a species was merely a hybrid, it’s hard to predict whether that might be enough to reinvigorate the conditions to foster ancient bacterial strains. Equally unknown, to what effect could archaic bacteria have on human health? 

Ultimately, there are theoretical arguments on both sides when it comes to the pros and cons of animal cloning of extinct animals. However, too many unknowns prevent us from truly knowing which side of the scale weighs the heaviest. 

Pros and Cons of Animal Cloning For Food 

Thus far, we’ve examined the pros and cons of animal cloning that can indirectly impact people’s daily lives. However, whether you realize it or not, it’s highly likely you’ve been experiencing the byproducts of animal cloning for years and didn’t even know it. 

With the breakthrough cloning of Dolly the Sheep, agricultural scientists realized cloning could duplicate prize breeding animals. Facing the potential to ensure greater yields and better meats, by the early 2000s, an entire industry surrounding the genetic modification of cows, pigs, and goats exploded on the scene. 

In truth, cloning is an expensive venture, so the overwhelming majority of livestock clones are used as breeding stock and not butchered for meat. Yet, it’s almost sure that aside from vegans, everyone has dined on beef that has come from the cloned offspring.

In 2008, the  U.S. Food and Drug Administration (FDA) declared  meat and milk from clones of cattle, swine, and goats to be “as safe to eat as food from conventionally bred animals.” Adding insult to injury for those expressing concerns, the FDA ruled that cloned food is not required to be labeled, preventing consumers’ ability to avoid meats coming from cloned animals. 

Criticizing the conclusions of the FDA’s 2008 “risk assessment,” opponents have argued cloning science is too new, not well understood, and too imprecise to adequately measure the risks. 

Pointing to their own study, the  Center for Food Safety  notes that even the FDA acknowledged in their risk assessment that “a vast quantity of animal clones are unhealthy and would not be suitable for the food supply.” 

Critics say that acknowledging the majority of cloned animals is not suitable for food supply but still approving the process for consumption; the FDA fails to address that defects in cloned animals can easily escape detection and enter human food supplies. A study performed by the National Academy of Sciences  (NAS) concluded that no method for detecting subtle health problems in clones exists. 

As the market for cloned livestock took off in the early 2000s, Sir Ian Wilmut, lead research scientist that cloned Dolly the Sheep,  expressed his reservations concerning science he helped develop being used for genetically enhanced foods. “Cattle cloners ought to be making systematic comparisons between clones and animals produced by embryo transfer, looking not just at their milk yield but also their health and lifespan,” said Wilmut. 

A 2013 study  concluded  that cloned cattle that reached adulthood and entered the food supply were essentially equivalent to conventional cattle concerning meat and milk quality. 

Consumer advocates also raise many concerns about the high doses of hormones and antibiotics used in the cloning process. Surprisingly little research has been done on the health effects of hormones used with cloned livestock, so the impact on human health isn’t entirely clear. 

Because the practice hasn’t been around long enough, the potential for adverse long-term effects from cloned food consumption is even less clear. 

Advocates of animal husbandry cloning  contend  the process allows for exact genetic copies of top breeding stock to be replicated, thereby producing healthier, superior livestock. 

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“Cloning reproduces the healthiest animals, thus minimizing the use of antibiotics, growth hormones and other chemicals,”  reads a statement  provided by the Biotechnology Industry Organization. “Consumers can benefit from cloning because meat and milk will be more healthful, consistent, and safe.” 

Like resurrecting long-dead species, the pros and cons of animal cloning for food sources are difficult to measure. The majority of public opinion has  never polled favorably  regarding cloning and animal husbandry. However, that alone doesn’t necessitate the practice is inherently harmful. 

Ultimately, unlike de-extinction cloning, livestock’s genetic engineering is very much a significant part of the modern agricultural industry. Whether or not this is a good or bad thing is a consequence we’ll likely have to live with, no matter the outcome. 

We’ve examined the pros and cons of animal cloning and how it affects human beings and the environment. However, the most contentious slippery slope surrounding the entire topic of animal cloning is the ethical debate and the potential negative consequences on the very animal life being used. 

Ethical Pros and Cons of Animal Cloning 

Is it morally right to create a life that would not otherwise come about naturally? When it comes to the pros and cons of animal cloning, this isn’t a question that can be answered by science or ground truth. As is the case with all moral issues, the ethical terrain surrounding animal cloning is complex. 

Yet, it’s arguably the most crucial question that vexes the public and genetic scientists alike. 

For some, there exists a principled argument against humanity effectively playing God, choosing life and death over other living creatures. For others, the ethical concerns center on more nuanced yet tangible and disturbingly brazen aspects of animal cloning. 

Arguably, the most compelling moral argument is the genuine suffering often endured by the animals involved in genetic science. The pain and suffering animals experience during cloning procedures, obstetrical complications that occur with surrogate mothers, and cloned animals’ health are genuine issues. 

Success rates of cloning procedures in producing live offspring, called “efficiency” in cloning science, are pretty grim. Studies have shown the differing efficiency rates based on the somatic cell type used, ranging from 30% to 93%, of clone pregnancies resulting in miscarriages. A  separate study  found that less than 5% of cloned embryos transferred into recipient cows survive. 

When live-births occur,   research has shown mortality rates to be as high as 50%. Basically, a coin toss decides if a cloned animal ends up dying within 130 days due to chronic health issues. 

The overwhelming bulk of past research on animal cloning involves examining the efficiency rates of somatic cell transfer, which  currently shows  success rates of 5%-20% for cows and 1%-5% for other species. Little research, however, exits on the health of cloned animals into adulthood. 

A  2016 study on cloned sheep, including four from the same cell lines as Dolly, found no evidence of late-onset, non-communicable diseases. “We could find no evidence, therefore, of a detrimental long-term effect of cloning by SCNT on the health of aged offspring among our cohort,” said the study’s authors. 

In light of the researcher’s findings, the proverbial elephant in the room is that when Dolly passed away at 6.5 years old from lung disease and severe arthritis, she had only lived around half of the typical 12-year life expectancy of a Finn Dorset sheep. 

Some  speculated  Dolly could have been born with the genetic age of the cell donor used to create her, who was six at the time of cell transfer. Researchers, however,  said they found no evidence  of Dolly being born at an advanced age, and her heirs have all gone on to live long, healthy lives. 

Adding an entirely new wrinkle in the ethical pros and cons of animal cloning, in 2019, scientists at the Institute of Neuroscience (ION) in Shanghai announced they had successfully  cloned five identical macaque monkeys . As if cloning human beings’ primate cousins weren’t already concerning, Chinese scientists purposefully cloned the macaque monkeys to suffer health issues. 

To unravel the mechanisms behind complex human disorders, such as Alzheimer’s, scientists at ION used gene-editing to disable a gene crucial to the monkey’s sleep-wake cycle. “Primates are the best animal model for studying higher cognitive functions and brain disorders in humans,” said neuroscientist Mu-ming Poo, ION’s director, and co-founder. 

With their five identical cloned monkeys, researchers at ION intend to study the effects of circadian rhythm disorders in hopes of better understanding and ultimately finding cures for human beings who suffer from sleep disorders. 

Initial results of the study on circadian rhythms using the cloned monkeys were published in the journal of National Science Review – of which Mu-ming Poo is Executive Editor-in-Chief. Poo said researchers did this because “the journal needs publicity” but denied being involved in the review process. 

An animal ethics statement published with the study reads, “The use and care of cynomolgus monkeys ( M .  fascicularis ) complied with the guidelines of the Animal Advisory Committee at the Shanghai Institutes for Biological Science, Chinese Academy of Sciences.” 

In 2019, Poo  said  Chinese researchers were already planning to use cloned primates to model other brain diseases, such as Alzheimer’s disease, Parkinson’s disease, a severe genetic intellectual disability called Angelman syndrome, and several genetic eye disorders. 

A statement issued by the People for the Ethical Treatment of Animals (PETA), an animal rights group based in Norfolk, Virginia, called ION’s research “a monstrous practice that causes [the monkeys] to suffer.” 

Whether it be for conservation, de-extinction, livestock use, or medical research, proponents solve animal cloning’s moral question by the adage, “the ends justify the means.” Specifically, the benefit to humanity through animal cloning outweighs any suffering and health-risk, or even purposeful manipulation to cause disease, caused through the cloning process. 

It’s vital to be abundantly clear. Just like the editors of Scientific American advocated using animal cloning for the conservation of endangered species, but shunned de-extinction, there is no single ethical solution amongst the varied domains of cloning science. 

The Debrief set out to examine the pros and cons of animal cloning. However, once one digs into the topic, one finds there is no simple answer. There is no universal conclusion as to whether cloning is fundamentally a positive or negative thing. 

There are compelling arguments on both sides, with some avenues, such as cloning for conservation, seemingly more acceptable. In these instances, realizing the alternative means the loss of an entire species can mitigate the pain, suffering, or low “efficiency” involved in the process. 

Meanwhile, other areas, such as cloning for medical research, even when that research may benefit humankind, leave one with a sense of disgust and simply feel morally wrong. 

Should science be involved in the cloning animals? Vote and let us know your thoughts in the comments. Make sure to check out The Debrief’s feature coming out today where we examine -The Pros and Cons of Animal Cloning. — The Debrief (@Debriefmedia) February 25, 2021

Some may argue that science is the quest for objective knowledge and should be divorced from ethical considerations. However, this view discounts the fact that, as the pursuers of knowledge, human beings are creatures capable of taking a holistic view and considering the broader consequences of their actions. 

Going back to Yellowstone National Park’s case, the overpopulation of deer and elk caused the depletion of natural resources, negatively impacting the entire ecosystem. Yet, these acts were not immoral, and the animals were incapable of measuring the consequences of their overconsumption. 

Conversely, human beings cannot claim such ignorance. We are more than capable of discerning the impact of our actions on ourselves and the world around us. We must use that holistic lens when examining animal cloning to measure risk vs. reward, both in the near and short term, and the principled impact on society. 

Ultimately, Dr. Shapiro best sums up the dilemma of animal cloning in her book, How to Clone a Mammoth: The Science of De-Extinction . Describing her work examining how to resurrect extinct species, Dr. Shapiro calls it “Exhilarating because of the unprecedented opportunities to understand life and boost conservation efforts, but terrifying in part for its ethical quandaries.”

Join us on Twitter or Facebook to weigh in and share your thoughts on the pros and cons of animal cloning. You can also follow all the latest  news and exciting feature content from The Debrief on Flipboard , Instagram , and don’t forget to subscribe to The Debrief YouTube Channel and check out The Official Debrief Podcast . 

Should science be involved in the cloning animals? Let us know your thoughts in the comments and make sure to check out… Posted by The Debrief on  Thursday, February 25, 2021

April 22, 2024

How a Cloned Ferret Inspired a DNA Bank for Endangered Species

The birth of a cloned black-footed ferret named Elizabeth Ann, and her two new sisters, has sparked a new pilot program to preserve the tissues of hundreds of endangered species “just in case”

By Cari Shane

Black-footed ferret clone Noreen.

Kika Tuff/Revive & Restore ( CC BY 4.0 )

Elizabeth Ann just became a triplet—at three years old.

This black-footed ferret ( Mustela nigripes )—the first endangered species in the U.S. to ever be successfully cloned—was joined late last year by her genetically identical baby sisters Antonia and Noreen , the U.S. Fish and Wildlife Service (FWS) announced Wednesday. All three come from the same cryogenically preserved cell line, obtained from a ferret named Willa, who lived in Wyoming in the 1980s.

As climate change, habitat loss and dwindling food supplies bring ever more endangered species “crashing to the brink,” a successful cloning such as this is a serious game changer, says Ben Novak, head of de-extinction efforts at Revive & Restore , a nonprofit outfit that applies biotechnology to conservation .

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Novak’s organization, along with ViaGen Pets & Equine and the San Diego Zoo Wildlife Alliance, is now teaming up with the FWS on a major project to cryogenically store tissue from every endangered species in the U.S., “just in case,” says Seth Willey , a FWS deputy assistant regional director who heads the project’s pilot phase. “It’s an insurance policy against future loss of biodiversity in the wild.”

It all began back in 1981 when scientists in Wyoming found and captured 18 black-footed ferrets—a species that had been thought to be extinct. A few of these animals bred in captivity, and their descendants were freed into the wild in an attempt to keep the species going. But scientists, worried about a future lack of genetic diversity in the fragile population , froze cells from Willa and one male, both of which had not bred naturally. The researchers wanted to bank this genetic material for potential later use to spice up the gene pool; they believed cloning would, in the future, become a practical reality.

Black-footed ferret clone Antonia.

Smithsonian Conservation Biology Institute ( CC BY 4.0 )

Now that it has, the FWS biobanking project aims to eventually collect tissue samples from at least one male and one female of every one of the hundreds of endangered animal species in the U.S. It will create a genetic library of sorts, akin to the Svalbard Global Seed Vault . The Svalbard program has been collecting seeds from all over the world since 2008 to safeguard and bank them—in a secure facility on a Norwegian Arctic island—in case they are needed for future food supplies. Though more than 1,600 U.S. plants and animals are listed as endangered or threatened, fewer than 14 percent have been cryopreserved. The new project is expected to provide a more systemized biobanking pipeline.

Because so many of today’s endangered species are already severely lacking in genetic diversity, saving their genes through tissue collection now could prevent extinction later. Beyond the black-footed ferret, there are few, if any, species for which cloning can bring back valuable diversity today. The known populations of the red wolf , Wyoming toad and Columbia Basin pygmy rabbit descend from just a handful of individuals captured for conservation breeding, Novak says. “People saved them..., [but] there is no single cell line or even tissue sample in a freezer somewhere. They didn’t collect them. They didn’t put them away,” he says. “To my knowledge at the current time, there is no equivalent to Elizabeth Ann” to act as a source of fresh genetic material in any other endangered species. And though it is likely too late for biobanking to work for some of those already bottlenecked populations, the project has other species, such as the northern long-eared bat and Penasco least chipmunk in it sights

Field biologists used a Sherman trap ( top left ) to capture an endangered Preble’s meadow jumping mouse ( Zapus hudsonius preblei ) and take a small skin sample for the biobanking project before releasing it back into a site where its habitat has been restored.

Kika Tuff/Revive & Restore

Field biologists from all over the country began collecting samples about six months before the pilot project was publicly announced in October 2023. The samples are saved in a cryogenic kit provided by Revive & Restore. Tissue is carefully obtained, usually from an animal’s ear, using a tool that looks like a paper hole punch; Novak says this doesn’t harm the animal. “The biologists working with endangered species are highly trained, and we have a rigorous permitting system to ensure animals do not face undue capture or stress,” Willey says.

Scientists will use these samples to generate cell lines that will produce millions of cells. These can be cryogenically preserved to give future scientists hundreds of thousands of cells with which to work. “Future recovery efforts decades from now have additional genetic rescue opportunities that otherwise would not exist,” Willey says. The genetic information will also be sequenced for use today by scientists working on captive breeding, climate resilience and other aspects of conservation.

A Mexican gray wolf ( Canis lupus baileyi ) is examined before its tissue is collected for the biobanking project.

Rebecca Bose/Wolf Conservation Center

Tissues from 13 endangered species have been collected so far, including from the New Mexico meadow jumping mouse , Peñasco least chipmunk , Texas kangaroo rat , Mexican wolf , Sonoran pronghorn and Mount Graham red squirrel . The goal for the pilot phase is 25 species in all. The samples are being stored at –256 degrees Fahrenheit at a U.S. Department of Agriculture cryogenic facility in Fort Collins, Colo.

Not all types of animals can currently be cloned because of cloning technology’s reliance on surrogates and live births. “For birds, laying hard-shelled eggs makes techniques like cloning and [in vitro fertilization] virtually impossible,” Novak says. Reptiles have similar limitations. “But if we have the cells, maybe there are things that we will be able to do in the coming decades that astonish everyone,” he says.Revive & Restore is looking at one approach called germ-line transfer for potential use with bird eggs. In this process, stem cells called primordial germ cells are isolated from a developing bird embryo and cultured in a petri dish. Through a small window in an eggshell, the cells are then transferred into another embryo that is at an early embryonic stage; the cells are injected directly into its bloodstream, where they circulate to developing testes or ovaries and become sperm or eggs. When this embryo becomes an adult, it uses these donated cells to reproduce, making it a surrogate parent.

Those involved in the biobanking project hope to extend it beyond the pilot. It’s a relatively inexpensive undertaking, says Novak, who hopes the U.S. Department of the Interior will provide $1.5 million dollars in funding.

Skin tissue is collected from a critically endangered Mexican gray wolf ( Canis lupus baileyi ).

Samantha Wisely, a population geneticist who isn’t involved with the biobanking project but is a member of a black-footed ferret genomics working group co-founded by Revive & Restore and the FWS, says that the U.S. should also help developing countries start similar programs to ensure conservation equity. And she notes the need to protect remaining critical habitats as well. “This is not going to save species if they don’t have habitat to be able to go back to,” says Wisely, who directs the Cervidae Health Research Initiative , a state-funded liaison between the deer farm industry and the University of Florida. Otherwise “it’s just a zoo in a petri dish, and I don’t think that’s what conservation is.”

Willey also underscores that biobanking is not a panacea—but rather a single item in the recovery toolbox. “Some people think if you have [species] in a freezer, you don’t need them in the wild,” he says. “That’s just not true.... We can’t lose what we have in the wild. But if we do, it’s good to have an insurance policy.”

Wisely agrees that biobanking is “an essential part of the puzzle.” And “if we don’t do it now,” she says, “we can’t do it later.”

Editor’s Note (4/24/24): This article was edited after posting to correct the description of other species that the biobanking project has in its sights and to clarify some of the organizations involved in the effort.

Innovative Cloning Advancements for Black-footed Ferret Conservation

DENVER — The U.S. Fish and Wildlife Service and its genetic research partners announce the birth of two new black-footed ferret clones – known as Noreen and Antonia – and are providing an update on their latest efforts to breed previously cloned black-footed ferret, Elizabeth Ann .   

Noreen was born at the National Black-footed Ferret Conservation Center in Colorado, while Antonia resides at the Smithsonian’s National Zoo & Conservation Biology Institute in Virginia. Both were cloned from the same genetic material as Elizabeth Ann. They are healthy and continue to reach expected developmental and behavioral milestones. The Service and its research partners plan to proceed with breeding efforts for Noreen and Antonia once they reach reproductive maturity later this year. This scientific advancement to clone the first U.S. endangered species is the result of an innovative partnership among the Service and critical species recovery partners and scientists at Revive & Restore, ViaGen Pets & Equine, Smithsonian’s National Zoo and Conservation Biology Institute, San Diego Zoo Wildlife Alliance, and the Association of Zoos and Aquariums. The application of this technology to endangered species addresses specific genetic diversity and disease concerns associated with black-footed ferrets. The Service views this new potential tool as one of many strategies to aid species recovery alongside efforts to address habitat challenges and other barriers to recovery. Elizabeth Ann remains healthy at the National Black-footed Ferret Conservation Center in northern Colorado, exhibiting typical adult ferret behavior. Planned efforts to breed Elizabeth Ann were unsuccessful due to a condition called hydrometra, where the uterine horn fills with fluid. Her other uterine horn was not fully developed, which is not unusual in other black-footed ferrets and therefore not believed to be linked to cloning. Elizabeth Ann otherwise remains in excellent health, symbolizing the early progress in biotechnology for species conservation.   

Elizabeth Ann, Noreen and Antonia were cloned from tissue samples collected in 1988 from a black-footed ferret known as Willa and stored at San Diego Zoo Wildlife Alliance’s Frozen Zoo. These samples contain three times more unique genetic variations than found on average in the current population. Introducing these currently unrepresented genes into the existing population would significantly benefit the species’ genetic diversity. All black-footed ferrets alive today, except the three clones, are descendants of the last seven wild individuals. This limited genetic diversity leads to unique challenges for their recovery. Besides genetic bottleneck issues, diseases like sylvatic plague and canine distemper further complicate recovery efforts. Cloning and related genetic research could offer potential solutions, aiding concurrent work on habitat conservation and reintroducing black-footed ferrets into the wild. Continuing genetic research for black-footed ferrets includes efforts to breed offspring from Noreen and Antonia, which would significantly increase the species’ genetic diversity. Collaborative work among partners also aims to achieve other long-term goals, such as developing resistance to sylvatic plague and potentially other diseases. Ongoing collaboration with innovative partners is driving scientific progress, underscoring the crucial role of conservation partnerships in safeguarding and improving American biodiversity. The Service will continue to provide updates as the research progresses. This research does not in any way supplant or diminish the Service’s efforts to recover the species in the wild. Those efforts, including reintroduction and monitoring of extant populations across the Great Plains, are ongoing, and the Service continues to collaborate with many partners working to conserve habitat for the species. More information about black-footed ferret conservation and biology is available from the Service’s National Black-footed Ferret Conservation Center and additional Questions and Answers related to this announcement.

________________________________________________________ Media contacts: U.S. Fish and Wildlife Service: Joe Szuszwalak, [email protected] Smithsonian: Annalisa Meyer, [email protected] San Diego Zoo Wildlife Alliance: Jake Gonzales, [email protected]   AZA: Betsy Hildebrandt, [email protected]   Revive & Restore: Kika Tuff, [email protected]   ViaGen Pets: Lauren Aston, [email protected]  

The U.S. Fish and Wildlife Service works with others to conserve, protect, and enhance fish, wildlife, plants, and their habitats for the continuing benefit of the American people. For more information, visit  www.fws.gov  and connect with us on social media: Facebook ,  Instagram ,  X (formerly known as Twitter),  LinkedIn ,  Flickr , and  YouTube . Revive & Restore is the leading wildlife conservation organization promoting the incorporation of biotechnologies into standard conservation practice. The Sausalito, California nonprofit was formed in 2012 with the idea that 21st century biotechnology can and should be used to enhance genetic diversity, build disease resistance, facilitate adaptation and more. Its mission is to enhance biodiversity through the genetic rescue of endangered and extinct species. www.reviverestore.org/bff   ViaGen Pets & Equine is the worldwide leader in cloning the animals we love. We provide the option of hope through DNA storage of your unique dog, cat or horse. Then through our amazing cloning technology we provide joy to clients all over the world with a genetic twin to their original animal. Our team is dedicated to providing outstanding service, quality animal care and a love that lasts forever. ViaGen Pets and Equine is dedicated to conversation through partnership efforts with the San Diego Zoo and Revive & Restore. www.viagenpets.com   San Diego Zoo Wildlife Alliance is a nonprofit conservation leader, inspiring passion for nature and collaboration for a healthier world. The Alliance supports innovative conservation science through global partnerships. Through wildlife care, science expertise and collaboration, more than 44 endangered species have been reintroduced to native habitats. Annually, the Alliance reaches over 1 billion people, in person at the San Diego Zoo and San Diego Zoo Safari Park, and virtually in 150 countries through media channels including San Diego Zoo Wildlife Explorers television program in children’s hospitals in 13 countries. Wildlife Allies – members, donors, guests – make success possible. www.sandiegozoowildlifealliance.org The Smithsonian’s National Zoo and Conservation Biology Institute (NZCBI) leads the Smithsonian’s global effort to save species, better understand ecosystems and train future generations of conservationists. Its two campuses are home to some of the world’s most critically endangered species. Always free of charge, the Zoo’s 163-acre park in the heart of Washington, D.C., features 2,100 animals representing 400 species and is a popular destination for children and families. At the Conservation Biology Institute’s 3,200-acre campus in Virginia, breeding and veterinary research on 250 animals representing 20 species provide critical data for the management of animals in human care and valuable insights for conservation of wild populations. NZCBI’s more than 300 staff and scientists work in Washington, D.C., Virginia and with partners at field sites across the United States and in more than 30 countries to save wildlife, collaborate with communities and conserve native habitats. NZCBI is a long-standing accredited member of the Association of Zoos and Aquariums. https://nationalzoo.si.edu   The Association of Zoos and Aquariums (AZA) , founded in 1924,is a nonprofit organization dedicated to the advancement of zoos and aquariums in the areas of conservation, animal wellbeing, education, science, and recreation. AZA is the accrediting body for the top zoos and aquariums in the United States and 12 other countries. Look for the AZA accreditation logo whenever you visit a zoo or aquarium as your assurance that you are supporting a facility dedicated to providing excellent care for animals, a great experience for you, and a better future for all living things. The AZA is a leader in saving species and your connection to helping animals all over the world. www.aza.org

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Two more black-footed ferrets are cloned, boosting hopes of saving an endangered species

This photo provided by Revive & Restore shows a cloned black-footed ferret named Noreen, Feb. 19, 2024, at the National Black-Footed Ferret Conservation Center in Carr, Colo. Two more black-footed ferrets, Noreen and Antonia, have been cloned from the genes used for the first endangered species clone in the U.S., bringing to three the number of slinky predators genetically identical to a single animal that was frozen back in the 1980s, the U.S. Fish and Wildlife Service announced Wednesday, April 17. (Kika Tuff/Revive & Restore via AP)

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CHEYENNE, Wyo. (AP) — Two more black-footed ferrets have been cloned from the genes used for the first clone of an endangered species in the U.S., bringing to three the number of slinky predators genetically identical to one of the last such animals found in the wild, the U.S. Fish and Wildlife Service announced Wednesday.

Efforts to breed the first clone , a female named Elizabeth Ann born in 2021, have failed, but the recent births of two more cloned females, named Noreen and Antonia, in combination with a captive breeding program launched in the 1980s, is boosting hopes of diversifying the endangered species. Genetic diversity can improve a species’ ability to adapt and survive despite disease outbreaks and changing environmental conditions.

Energetic and curious, black-footed ferrets are a nocturnal type of weasel with dark eye markings resembling a robber’s mask. Their prey is prairie dogs, and the ferrets hunt the rodents in often vast burrow colonies on the plains.

Black-footed ferrets are now a conservation success story — after being all but wiped out in the wild, thousands of them have been bred in captivity and reintroduced at dozens of sites in the western U.S., Canada and Mexico since the 1990s.

Because they feed exclusively on prairie dogs, they have been victims of farmer and rancher efforts to poison and shoot the land-churning rodents — so much so that they were thought to be extinct, until a ranch dog named Shep brought a dead one home in western Wyoming in 1981. Conservationists then managed to capture seven more, and establish a breeding program.

But their gene pool is small — all known black-footed ferrets today are descendants of those seven animals — so diversifying the species is critically important.

Noreen and Antonia, like Elizabeth Ann , are genetically identical to Willa, one of the original seven. Willa’s remains -- frozen back in the 1980s and kept at the San Diego Zoo Wildlife Alliance’s Frozen Zoo -- could help conservation efforts because her genes contain roughly three times more unique variations than are currently found among black-footed ferrets, according to the Fish and Wildlife Service.

Elizabeth Ann still lives at the National Black-footed Ferret Conservation Center in Fort Collins, Colorado, but she’s been unable to breed, due to a reproductive organ issue that isn’t a result of being cloned, the Fish and Wildlife Service said in a statement.

Biologists plan to try to breed Noreen and Antonia after they reach maturity later this year.

The ferrets were born at the ferret conservation center last May. The Fish and Wildlife Service waited almost year to announce the births amid ongoing scientific work, other black-footed ferret breeding efforts and the agency’s other priorities, Fish and Wildlife Service spokesman Joe Szuszwalak said by email.

“Science takes time and does not happen instantaneously,” Szuszwalak wrote.

Cloning makes a new plant or animal by copying the genes of an existing animal. To clone these three ferrets, the Fish and Wildlife Service worked with zoo and conservation organizations and ViaGen Pets & Equine, a Texas business that clones horses for $85,000 and pet dogs for $50,000.

The company also has cloned a Przewalski’s wild horse , a species from Mongolia.

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National Academy of Sciences (US), National Academy of Engineering (US), Institute of Medicine (US) and National Research Council (US) Committee on Science, Engineering, and Public Policy. Scientific and Medical Aspects of Human Reproductive Cloning. Washington (DC): National Academies Press (US); 2002.

Scientific and Medical Aspects of Human Reproductive Cloning.

• Hardcopy Version at National Academies Press

2 Cloning: Definitions And Applications

In this chapter, we address the following questions in our task statement:

What does cloning of animals including humans mean? What are its purposes? How does it differ from stem cell research?

To organize its response to those questions, the panel developed a series of subquestions, which appear as the section headings in the following text.

• WHAT IS MEANT BY REPRODUCTIVE CLONING OF ANIMALS INCLUDING HUMANS?

Reproductive cloning is defined as the deliberate production of genetically identical individuals. Each newly produced individual is a clone of the original. Monozygotic (identical) twins are natural clones. Clones contain identical sets of genetic material in the nucleus—the compartment that contains the chromosomes—of every cell in their bodies. Thus, cells from two clones have the same DNA and the same genes in their nuclei.

All cells, including eggs, also contain some DNA in the energy-generating “factories” called mitochondria. These structures are in the cytoplasm, the region of a cell outside the nucleus. Mitochondria contain their own DNA and reproduce independently. True clones have identical DNA in both the nuclei and mitochondria, although the term clones is also used to refer to individuals that have identical nuclear DNA but different mitochondrial DNA.

• HOW IS REPRODUCTIVE CLONING DONE?

Two methods are used to make live-born mammalian clones. Both require implantation of an embryo in a uterus and then a normal period of gestation and birth. However, reproductive human or animal cloning is not defined by the method used to derive the genetically identical embryos suitable for implantation. Techniques not yet developed or described here would nonetheless constitute cloning if they resulted in genetically identical individuals of which at least one were an embryo destined for implantation and birth.

The two methods used for reproductive cloning thus far are as follows:

• Cloning using somatic cell nuclear transfer ( SCNT ) [ 1 ]. This procedure starts with the removal of the chromosomes from an egg to create an enucleated egg. The chromosomes are replaced with a nucleus taken from a somatic (body) cell of the individual or embryo to be cloned. This cell could be obtained directly from the individual, from cells grown in culture, or from frozen tissue. The egg is then stimulated, and in some cases it starts to divide. If that happens, a series of sequential cell divisions leads to the formation of a blastocyst, or preimplantation embryo. The blastocyst is then transferred to the uterus of an animal. The successful implantation of the blastocyst in a uterus can result in its further development, culminating sometimes in the birth of an animal. This animal will be a clone of the individual that was the donor of the nucleus. Its nuclear DNA has been inherited from only one genetic parent.

The number of times that a given individual can be cloned is limited theoretically only by the number of eggs that can be obtained to accept the somatic cell nuclei and the number of females available to receive developing embryos. If the egg used in this procedure is derived from the same individual that donates the transferred somatic nucleus, the result will be an embryo that receives all its genetic material—nuclear and mitochondrial—from a single individual. That will also be true if the egg comes from the nucleus donor's mother, because mitochondria are inherited maternally. Multiple clones might also be produced by transferring identical nuclei to eggs from a single donor. If the somatic cell nucleus and the egg come from different individuals, they will not be identical to the nuclear donor because the clones will have somewhat different mitochondrial genes [ 2 ; 3 ]

• Cloning by embryo splitting. This procedure begins with in vitro fertilization ( IVF ): the union outside the woman's body of a sperm and an egg to generate a zygote. The zygote (from here onwards also called an embryo) divides into two and then four identical cells. At this stage, the cells can be separated and allowed to develop into separate but identical blastocysts, which can then be implanted in a uterus. The limited developmental potential of the cells means that the procedure cannot be repeated, so embryo splitting can yield only two identical mice and probably no more than four identical humans.

The DNA in embryo splitting is contributed by germ cells from two individuals—the mother who contributed the egg and the father who contributed the sperm. Thus, the embryos, like those formed naturally or by standard IVF , have two parents. Their mitochondrial DNA is identical. Because this method of cloning is identical with the natural formation of monozygotic twins and, in rare cases, even quadruplets, it is not discussed in detail in this report.

• WILL CLONES LOOK AND BEHAVE EXACTLY THE SAME?

Even if clones are genetically identical with one another, they will not be identical in physical or behavioral characteristics, because DNA is not the only determinant of these characteristics. A pair of clones will experience different environments and nutritional inputs while in the uterus, and they would be expected to be subject to different inputs from their parents, society, and life experience as they grow up. If clones derived from identical nuclear donors and identical mitocondrial donors are born at different times, as is the case when an adult is the donor of the somatic cell nucleus, the environmental and nutritional differences would be expected to be more pronounced than for monozygotic (identical) twins. And even monozygotic twins are not fully identical genetically or epigenetically because mutations, stochastic developmental variations, and varied imprinting effects (parent-specific chemical marks on the DNA) make different contributions to each twin [ 3 ; 4 ].

Additional differences may occur in clones that do not have identical mitochondria. Such clones arise if one individual contributes the nucleus and another the egg—or if nuclei from a single individual are transferred to eggs from multiple donors. The differences might be expected to show up in parts of the body that have high demands for energy—such as muscle, heart, eye, and brain—or in body systems that use mitochondrial control over cell death to determine cell numbers [ 5 ; 6 ].

• WHAT ARE THE PURPOSES OF REPRODUCTIVE CLONING?

Cloning of livestock [ 1 ] is a means of replicating an existing favorable combination of traits, such as efficient growth and high milk production, without the genetic “lottery” and mixing that occur in sexual reproduction. It allows an animal with a particular genetic modification, such as the ability to produce a pharmaceutical in milk, to be replicated more rapidly than does natural mating [ 7 ; 8 ]. Moreover, a genetic modification can be made more easily in cultured cells than in an intact animal, and the modified cell nucleus can be transferred to an enucleated egg to make a clone of the required type. Mammals used in scientific experiments, such as mice, are cloned as part of research aimed at increasing our understanding of fundamental biological mechanisms.

In principle, those people who might wish to produce children through human reproductive cloning [ 9 ] include:

• Infertile couples who wish to have a child that is genetically identical with one of them, or with another nucleus donor
• Other individuals who wish to have a child that is genetically identical with them, or with another nucleus donor
• Parents who have lost a child and wish to have another, genetically identical child
• People who need a transplant (for example, of cord blood) to treat their own or their child's disease and who therefore wish to collect genetically identical tissue from a cloned fetus or newborn.

Possible reasons for undertaking human reproductive cloning have been analyzed according to their degree of justification. For example, in reference 10 it is proposed that human reproductive cloning aimed at establishing a genetic link to a gametically infertile parent would be more justifiable than an attempt by a sexually fertile person aimed at choosing a specific genome.

Transplantable tissue may be available without the need for the birth of a child produced by cloning. For example, embryos produced by in vitro fertilization ( IVF ) can be typed for transplant suitability, and in the future stem cells produced by nuclear transplantation may allow the production of transplantable tissue.

The alternatives open to infertile individuals are discussed in Chapter 4 .

• HOW DOES REPRODUCTIVE CLONING DIFFER FROM STEM CELL RESEARCH?

The recent and current work on stem cells that is briefly summarized below and discussed more fully in a recent report from the National Academies entitled Stem Cells and the Future of Regenerative Medicine [ 11 ] is not directly related to human reproductive cloning. However, the use of a common initial step—called either nuclear transplantation or somatic cell nuclear transfer ( SCNT )—has led Congress to consider bills that ban not only human reproductive cloning but also certain areas of stem cell research. Stem cells are cells that have the ability to divide repeatedly and give rise to both specialized cells and more stem cells. Some, such as some blood and brain stem cells, can be derived directly from adults [ 12 - 19 ] and others can be obtained from preimplantation embryos. Stem cells derived from embryos are called embryonic stem cells ( ES cells ). The above-mentioned report from the National Academies provides a detailed account of the current state of stem cell research [ 11 ].

ES cells are also called pluripotent stem cells because their progeny include all cell types that can be found in a postimplantation embryo, a fetus, and a fully developed organism. They are derived from the inner cell mass of early embryos (blastocysts) [ 20 - 23 ]. The cells in the inner cell mass of a given blastocyst are genetically identical, and each blastocyst yields only a single ES cell line. Stem cells are rarer [ 24 ] and more difficult to find in adults than in preimplantation embryos, and it has proved harder to grow some kinds of adult stem cells into cell lines after isolation [ 25 ; 26 ].

Production of different cells and tissues from ES cells or other stem cells is a subject of current research [ 11 ; 27 - 31 ]. Production of whole organs other than bone marrow (to be used in bone marrow transplantation) from such cells has not yet been achieved, and its eventual success is uncertain.

Current interest in stem cells arises from their potential for the therapeutic transplantation of particular healthy cells, tissues, and organs into people suffering from a variety of diseases and debilitating disorders. Research with adult stem cells indicates that they may be useful for such purposes, including for tissues other than those from which the cells were derived [ 12 ; 14 ; 17 ; 18 ; 25 - 27 ; 32 - 43 ]. On the basis of current knowledge, it appears unlikely that adults will prove to be a sufficient source of stem cells for all kinds of tissues [ 11 ; 44 - 47 ]. ES cell lines are of potential interest for transplantation because one cell line can multiply indefinitely and can generate not just one type of specialized cell, but many different types of specialized cells (brain, muscle, and so on) that might be needed for transplants [ 20 ; 28 ; 45 ; 48 ; 49 ]. However, much more research will be needed before the magnitude of the therapeutic potential of either adult stem cells or ES cells will be well understood.

One of the most important questions concerning the therapeutic potential of stem cells is whether the cells, tissues, and perhaps organs derived from them can be transplanted with minimal risk of transplant rejection. Ideally, adult stem cells advantageous for transplantation might be derived from patients themselves. Such cells, or tissues derived from them, would be genetically identical with the patient's own and not be rejected by the immune system. However, as previously described, the availability of sufficient adult stem cells and their potential to give rise to a full range of cell and tissue types are uncertain. Moreover, in the case of a disorder that has a genetic origin, a patient's own adult stem cells would carry the same defect and would have to be grown and genetically modified before they could be used for therapeutic transplantation.

The application of somatic cell nuclear transfer or nuclear transplantation offers an alternative route to obtaining stem cells that could be used for transplantation therapies with a minimal risk of transplant rejection. This procedure—sometimes called therapeutic cloning, research cloning, or nonreproductive cloning, and referred to here as nuclear transplantation to produce stem cells —would be used to generate pluripotent ES cells that are genetically identical with the cells of a transplant recipient [ 50 ]. Thus, like adult stem cells, such ES cells should ameliorate the rejection seen with unmatched transplants.

Two types of adult stem cells—stem cells in the blood forming bone marrow and skin stem cells—are the only two stem cell therapies currently in use. But, as noted in the National Academies' report entitled Stem Cells and the Future of Regenerative Medicine , many questions remain before the potential of other adult stem cells can be accurately assessed [ 11 ]. Few studies on adult stem cells have sufficiently defined the stem cell's potential by starting from a single, isolated cell, or defined the necessary cellular environment for correct differentiation or the factors controlling the efficiency with which the cells repopulate an organ. There is a need to show that the cells derived from introduced adult stem cells are contributing directly to tissue function, and to improve the ability to maintain adult stem cells in culture without the cells differentiating. Finally, most of the studies that have garnered so much attention have used mouse rather than human adult stem cells.

ES cells are not without their own potential problems as a source of cells for transplantation. The growth of human ES cells in culture requires a “feeder” layer of mouse cells that may contain viruses, and when allowed to differentiate the ES cells can form a mixture of cell types at once. Human ES cells can form benign tumors when introduced into mice [ 20 ], although this potential seems to disappear if the cells are allowed to differentiate before introduction into a recipient [ 51 ]. Studies with mouse ES cells have shown promise for treating diabetes [ 30 ], Parkinson's disease [ 52 ], and spinal cord injury [ 53 ].

The ES cells made with nuclear transplantation would have the advantage over adult stem cells of being able to provide virtually all cell types and of being able to be maintained in culture for long periods of time. Current knowledge is, however, uncertain, and research on both adult stem cells and stem cells made with nuclear transplantation is required to understand their therapeutic potentials. (This point is stated clearly in Finding and Recommendation 2 of Stem Cells and the Future of Regenerative Medicine [ 11 ] which states, in part, that “studies of both embryonic and adult human stem cells will be required to most efficiently advance the scientific and therapeutic potential of regenerative medicine.”) It is likely that the ES cells will initially be used to generate single cell types for transplantation, such as nerve cells or muscle cells. In the future, because of their ability to give rise to many cell types, they might be used to generate tissues and, theoretically, complex organs for transplantation. But this will require the perfection of techniques for directing their specialization into each of the component cell types and then the assembly of these cells in the correct proportion and spatial organization for an organ. That might be reasonably straightforward for a simple structure, such as a pancreatic islet that produces insulin, but it is more challenging for tissues as complex as that from lung, kidney, or liver [ 54 ; 55 ].

The experimental procedures required to produce stem cells through nuclear transplantation would consist of the transfer of a somatic cell nucleus from a patient into an enucleated egg, the in vitro culture of the embryo to the blastocyst stage, and the derivation of a pluripotent ES cell line from the inner cell mass of this blastocyst. Such stem cell lines would then be used to derive specialized cells (and, if possible, tissues and organs) in laboratory culture for therapeutic transplantation. Such a procedure, if successful, can avoid a major cause of transplant rejection. However, there are several possible drawbacks to this proposal. Experiments with animal models suggest that the presence of divergent mitochondrial proteins in cells may create “minor” transplantation antigens [ 56 ; 57 ] that can cause rejection [ 58 - 63 ]; this would not be a problem if the egg were donated by the mother of the transplant recipient or the recipient herself. For some autoimmune diseases, transplantation of cells cloned from the patient's own cells may be inappropriate, in that these cells can be targets for the ongoing destructive process. And, as with the use of adult stem cells, in the case of a disorder that has a genetic origin, ES cells derived by nuclear transplantation from the patient's own cells would carry the same defect and would have to be grown and genetically modified before they could be used for therapeutic transplantation. Using another source of stem cells is more likely to be feasible (although immunosuppression would be required) than the challenging task of correcting the one or more genes that are involved in the disease in adult stem cells or in a nuclear transplantation-derived stem cell line initiated with a nucleus from the patient.

In addition to nuclear transplantation, there are two other methods by which researchers might be able to derive ES cells with reduced likeli hood for rejection. A bank of ES cell lines covering many possible genetic makeups is one possibility, although the National Academies report entitled Stem Cells and the Future of Regenerative Medicine rated this as “difficult to conceive” [ 11 ]. Alternatively, embryonic stem cells might be engineered to eliminate or introduce certain cell-surface proteins, thus making the cells invisible to the recipient's immune system. As with the proposed use of many types of adult stem cells in transplantation, neither of these approaches carries anything close to a promise of success at the moment.

The preparation of embryonic stem cells by nuclear transplantation differs from reproductive cloning in that nothing is implanted in a uterus. The issue of whether ES cells alone can give rise to a complete embryo can easily be misinterpreted. The titles of some reports suggest that mouse embryos can be derived from ES cells alone [ 64 - 72 ]. In all cases, however, the ES cells need to be surrounded by cells derived from a host embryo, in particular trophoblast and primitive endoderm. In addition to forming part of the placenta, trophoblast cells of the blastocyst provide essential patterning cues or signals to the embryo that are required to determine the orientation of its future head and rump (anterior-posterior) axis. This positional information is not genetically determined but is acquired by the trophoblast cells from events initiated soon after fertilization or egg activation. Moreover, it is critical that the positional cues be imparted to the inner cells of the blastocyst during a specific time window of development [ 73 - 76 ]. Isolated inner cell masses of mouse blastocysts do not implant by themselves, but will do so if combined with trophoblast vesicles from another embryo [ 77 ]. By contrast, isolated clumps of mouse ES cells introduced into trophoblast vesicles never give rise to anything remotely resembling a postimplantation embryo, as opposed to a disorganized mass of trophoblast. In other words, the only way to get mouse ES cells to participate in normal development is to provide them with host embryonic cells, even if these cells do not remain viable throughout gestation (Richard Gardner, personal communication). It has been reported that human [ 20 ] and primate [ 78 - 79 ] ES cells can give rise to trophoblast cells in culture. However, these trophoblast cells would presumably lack the positional cues normally acquired during the development of a blastocyst from an egg. In the light of the experimental results with mouse ES cells described above, it is very unlikely that clumps of human ES cells placed in a uterus would implant and develop into a fetus. It has been reported that clumps of human ES cells in culture, like clumps of mouse ES cells, give rise to disorganized aggregates known as embryoid bodies [ 80 ].

Besides their uses for therapeutic transplantation, ES cells obtained by nuclear transplantation could be used in laboratories for several types of studies that are important for clinical medicine and for fundamental research in human developmental biology. Such studies could not be carried out with mouse or monkey ES cells and are not likely to be feasible with ES cells prepared from normally fertilized blastocysts. For example, ES cells derived from humans with genetic diseases could be prepared through nuclear transplantation and would permit analysis of the role of the mutated genes in both cell and tissue development and in adult cells difficult to study otherwise, such as nerve cells of the brain. This work has the disadvantage that it would require the use of donor eggs. But for the study of many cell types there may be no alternative to the use of ES cells; for these cell types the derivation of primary cell lines from human tissues is not yet possible.

If the differentiation of ES cells into specialized cell types can be understood and controlled, the use of nuclear transplantation to obtain genetically defined human ES cell lines would allow the generation of genetically diverse cell lines that are not readily obtainable from embryos that have been frozen or that are in excess of clinical need in IVF clinics. The latter do not reflect the diversity of the general population and are skewed toward genomes from couples in which the female is older than the period of maximal fertility or one partner is infertile. In addition, it might be important to produce stem cells by nuclear transplantation from individuals who have diseases associated with both simple [81] and complex (multiple-gene) heritable genetic predilections. For example, some people have mutations that predispose them to “Lou Gehrig's disease” (amyotrophic lateral sclerosis, or ALS); however, only some of these individuals become ill, presumably because of the influence of additional genes. Many common genetic predilections to diseases have similarly complex etiologies; it is likely that more such diseases will become apparent as the information generated by the Human Genome Project is applied. It would be possible, by using ES cells prepared with nuclear transplantation from patients and healthy people, to compare the development of such cells and to study the fundamental processes that modulate predilections to diseases.

Neither the work with ES cells , nor the work leading to the formation of cells and tissues for transplantation, involves the placement of blastocysts in a uterus. Thus, there is no embryonic development beyond the 64 to 200 cell stage, and no fetal development.

2-1. Reproductive cloning involves the creation of individuals that contain identical sets of nuclear genetic material ( DNA ). To have complete genetic identity, clones must have not only the same nuclear genes, but also the same mitochondrial genes.

2-2. Cloned mammalian animals can be made by replacing the chromosomes of an egg cell with a nucleus from the individual to be cloned, followed by stimulation of cell division and implantation of the resulting embryo.

2-3. Cloned individuals, whether born at the same or different times, will not be physically or behaviorally identical with each other at comparable ages.

2-4. Stem cells are cells that have an extensive ability to self-renew and differentiate, and they are therefore important as a potential source of cells for therapeutic transplantation. Embryonic stem cells derived through nuclear transplantation into eggs are a potential source of pluripotent (embryonic) stem cell lines that are immunologically similar to a patient's cells. Research with such cells has the goal of producing cells and tissues for therapeutic transplantation with minimal chance of rejection.

2-5. Embryonic stem cells and cell lines derived through nuclear transplantation could be valuable for uses other than organ transplantation. Such cell lines could be used to study the heritable genetic components associated with predilections to a variety of complex genetic diseases and test therapies for such diseases when they affect cells that are hard to study in isolation in adults.

2-6. The process of obtaining embryonic stem cells through nuclear transplantation does not involve the placement of an embryo in a uterus, and it cannot produce a new individual.

• Cite this Page National Academy of Sciences (US), National Academy of Engineering (US), Institute of Medicine (US) and National Research Council (US) Committee on Science, Engineering, and Public Policy. Scientific and Medical Aspects of Human Reproductive Cloning. Washington (DC): National Academies Press (US); 2002. 2, Cloning: Definitions And Applications.
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