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Cloning - General Information

The type of cloning which we will focus on here is called Nuclear Transfer (NT) which is the creation of one or more genetically identical animals by transferring the nucleus of a body cell into an egg from which the nucleus has been removed. This is also known as or cell nuclear replacement (CNR).

3D cell

What is cloning? Are ther different types?

When people see the word “clone” used, many questions come to mind. Cloning occurs naturally in plants when bulbs colonize in the area around a parent plant. Cloning can be described as:

  • A group of genetically identical cells produced by mitotic division from an original cell. This is where the cell creates anew set of chromosomes and splits into two daughter cells. This is how replacement cells are produced in your body when the old ones wear out.
  • A group of DNA molecules produced from an original length of DNA sequences produced by a bacterium or a virus using molecular biology techniques. This is what is often called molecular cloning or DNA cloning.
  • The production of genetically identical animals by 'embryo splitting'. This can occur naturally at the two cell stage to give identical twins. In cattle, when individual cells from 4- and 8-cell embryos and implanted in different foster mothers, where they can develop normally into calves.

What animals have been cloned?

The modern cloning techniques involving nuclear transfers have been successfully performed on several species: (in chronological order)

  • 1963 – Fish, the first to allegedly clone a carp, China.

    In 1963, an Asian scientist, embryologist Tong Dizhou, allegedly cloned a fish in1963, thirty-three years before “Dolly,” the sheep. He published the findings in an obscure Chinese science journal, which was never translated into English.

  • 1996 – Sheep, the first animal cloned, Roslin Institute, England.

    In 1996, the Roslin Institute, England cloned “Dolly,” a sheep to demonstrate that somatic cells were able to be used as donor cells for the procedure, prior to this blastoceles (stem cells) were used in nuclear transfer technology.

  • 1997 – Mouse, the first cloned mouse, University of Hawaii.

    1997, University of Hawai'i at Manoa cloned “Cumulina,” a mouse, in the laboratory of Ryuzo Yanagimachi. Mice were used as a cloning model to perfect techniques used in nuclear transfer, as well as to understand the type of somatic cell used.

  • 1999 – Cow, cloned cow gives birth, University of Connecticut.

    In 1999, University of Connecticut cloned the cow “Daisy” from a donor that was past menopause, which demonstrated the ability of the nuclear transfer technique to reverse cellular aging.

  • 1999 – Goat, first cloned transgenic goats, Louisiana State University.

    In 1999, Louisiana State University cloned “Millie,” the first transgenic goat, which means that she carries one gene of a different species. In this case, this goat is special because her milk contains a therapeutic protein that could be extracted to make a drug for patients undergoing coronary bypass surgery.

  • 2000 – Monkey, from Oregon Regional Primate Research Centre.

    In 2000, Oregon Regional Primate Research Centre cloned “Tetra,” a rhesus monkey, using a method that splits the original cells in an embryo to create multiple identical animals, a process described as artificial twinning.

  • 2000 – Pig, from PPL Therapeutics Plc .

    In 2000, PPL Therapeutics Plc, cloned five female piglets named Millie, Christa, Alexis, Carrel, and Dotcom, in Blacksburg, Virginia. Nuclear transfer in pigs marks a leap forward in the technology, and moved the company closer to its goal of producing animals whose organs and cells could be successfully transplanted into humans.

  • 2001 – Cat, from Texas A&M University.

    In 2001, Texas A&M University “Copy Cat,” cat. Techniques developed to clone this feline species will facilitate the future cloning of domestic housecats.

  • 2001 – Gaur, endangered ox-like animal, by Advanced Cell Technology.

    In 2001, Advanced Cell Technologies, Massachusetts cloned “Noah,” a species of ox called gaur. This was the first endangered species to be cloned as a part of a conservation project.

  • 2001 – Mouflon, endangered sheep, by University of Teramo, Italy.

    In 2001, University of Teramo, Italy cloned a mouflon, an endangered species of wild sheep found in the Mediterranean. The lamb is a kind of hybrid, with genomic and mitochondrial DNA from two different species to help preserve this endangered species.

  • 2002 – Rabbit, from Agronomy Research Institute, France.

    In 2002, Agronomy Research Institute, France cloned a rabbit. Rabbits are often used as a means to study human disease as well as a ‘pharming’, or the collection of transgene products produced within a living organism.

  • 2003 – Mule, from University of Idaho and Utah State University.

    In 2003, University of Idaho and Utah State University cloned the first mule, “Idaho Gem.” Mules are a hybrid cross between a male donkey and a female horse and are commonly sterile. This makes reproduction possible in a species that is incapable.

  • 2003 – Rat, researchers from China and France.

    In 2003, researchers from Institute of Zoology, China and Agronomy Research Institute, France cloned “Ralph,” a rat. Cloned rats are used to study several human diseases and enable researchers to engineer diseases for more comprehensive research.

  • 2003 – Deer, from Texas A&M University.

    In 2003, Texas A&M University cloned a deer, “Dewey.” The successful cloning of deer could lead to the preservation of endangered deer species in the southern United States.

  • 2003 – Horse, from Laboratory of Reproductive Technology, Italy.

    In 2003, the Laboratory of Reproductive Technology, Italy cloned “Prometea,” the first horse. Cloning could aid in reproducing successful gelding show horses that have no ability to reproduce normally.

  • 2004 – Fruit flies, from Dalhousie University, Canada.

    In 2004, Dalhousie University, Canada cloned the first fruit fly. Fruit flies are an excellent model for the study of several biological mechanisms, including reproduction. Understanding nuclear transfer in the fruit fly may lead to improvement in the success of cloning.

  • 2005 – Dog, from Seoul National University, South Korea.

    In 2005, Seoul National University, South Korea cloned “Snuppy,” a dog. Dogs suffer from a variety of diseases similar to humans, and the cloning of dogs will allow for the better studying of these diseases.

  • 2005 – Water Buffalo, from China Agricultural University, Beijing.

    In 2005, China Agricultural University, Beijing cloned Water Buffalo. The cloning of this species is used to generate buffalo with superior genetic traits that would bolster the genetics of local breeds.

  • 2006 – Ferret, from University of Iowa .

    In 2006, University of Iowa cloned the first ferret. Cloned ferrets are being used as a model to study cystic fibrosis and other human respiratory diseases.

Who has been involved in cloning?

  • 1938 - German Nobel Laureate Hans Spemann.

    1938 - German Nobel Laureate Hans Spemann proposes an experiment involving the placement of a nucleus into an enucleated oocyte. Spemann did not perform the experiment due to lack of proper equipment. Spemann’s idea later became the basis for the nuclear transfer procedure (Spemann 1938).

  • 1952 – Scientists Robert Briggs and Thomas J. King.

    1952 - Scientists Robert Briggs and Thomas J. King were the first to successfully produce nuclear transferred amphibian offspring when they produced Northern Leopard Frog tadpoles (Briggs and King 1952).

  • 1966 – Sir John B. Gurdon and V. Uehlinger.

    1966 - Sir John B. Gurdon and V. Uehlinger used frog larval nuclei to produce fertile nuclear transferred Xenopus frogs (Gurdon and Uehlinger 1966).

  • 1975 - The beginning trials of somatic cell nuclear transfer in frogs.

    1975 - The beginning trials of somatic cell nuclear transfer in frogs provided evidence that adult cells were able to de-differentiate and produce normal tadpoles, however there were none that survived to adulthood. Somatic cells came from several origins including skin, lymphocytes, erythrocytes, leukocytes and erythroblasts (Gurdon et al. 1975, Wabl et al. 1975, Di Berardino and Hoffner 1983, Di Berardino and Orr 1992).

  • 1986 - Danish scientist Steen Willadsen cloned first farm animal.

    1986 - Danish scientist Steen Willadsen produced viable live lambs by taking 8-16 cell blastomeres and transferring them into enucleated oocytes (Willadsen 1986).

  • 1987 – First, Prather, and Eyestone cloned a cow.

    1987 - Neal First, Randal Prather, and Willard Eyestone, working at the University of Wisconsin, used early embryonic cells to produce nuclear transferred cattle. Through the next few years many species were cloned from early embryonic cells including mice, rats, rabbits, pigs, goats and monkeys (Prather et al. 1987, Di Berardino 2001).

  • 1994 - Sims and First produced calves.

    1994 - M. Sims and N.L. First produced cloned calves by taking cells from the inner cell mass then culturing them in vitro up to twenty eight days prior to the nuclear transfer (Sims and First 1994).

  • 1996 – Biologist Keith Campbell involved in cloning sheep.

    1996 - Biologist Keith Campbell announced he had produced five cloned sheep using in vitro cultured, putative differentiated inner cell mass cells (Campbell et al. 1996).

  • 1997 - Scientists at the Roslin Institute cloned Dolly the sheep.

    1997 - Scientists at the Roslin Institute in Scotland announced the world’s first cloned animal from an adult cell. Dolly the sheep was produced by Ian Wilmut and others at the Roslin Institute used cell from the udder of an adult ewe. This was significant in that it demonstrated that a completely differentiated cell was capable of being reprogrammed to an embryonic state and form a live animal (Wilmut et al. 1997).

  • 1998 - Wakayama and others produced a mouse.

    1998 - A group of researchers headed by Wakayama produced a mouse from adult somatic cells (Wakayama et al. 1998).

  • 1999 - Wells and others produced a cow.

    1999 - A group of researchers headed by Wells produced a cow from adult somatic cells. Bagusisi and colleagues produced a goat via somatic cell nuclear transfer (Wells et al. 1999).

  • 2000 - Polejaeva produced a pig.

    2000 - A group of researchers headed by Polejaeva produced a pig from adult somatic cells (Polejaeva et al. 2000).

  • 2001 - Loi produced a mouflon sheep.

    2001 - A group of researchers headed by Loi produced a mouflon sheep from adult somatic cells (Loi et al. 2001).

  • 2002 – Chesne and Chin produced a rabbit and cat, respectively.

    2002 - A group of researchers headed by Chesne produced a rabbit from adult somatic cells. At the same time a group headed by Shin produced a cat from adult somatic cells (Chesne et al. 2002, Shin et al. 2002).

  • 2003 – Woods and White produced the first mules.

    2003 - In collaboration between researchers Gordon Woods at the University of Idaho and Kenneth White from Utah State University the first mules were produced using somatic cell nuclear transfer. Also this year a group of researchers headed by Zhou produced a rat from adult somatic cells. A group from Italy headed by Galli produced the first horse clone using somatic cell nuclear transfer (Woods et al. 2003, Zhou et al. 2003, Galli et al. 2003).

  • 2005 – Lee produced a dog.

    2005 - A group of researchers headed by Lee produced a dog from adult somatic cells (Lee et al. 2005).

  • 2006 – Li produced a ferret.

    2006 - A group of researchers headed by Li produced a ferret from adult somatic cells (Li et al. 2006).