For the cloning of human beings see Human cloning. For other uses see Cloning (disambiguation). The sea anemone Anthopleura elegantissima in process of cloning

Cloning in biology is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria insects or plants reproduce asexually. Cloning in biotechnology refers to processes used to create copies of DNA fragments (molecular cloning) cells (cell cloning) or organisms. The term also refers to the production of multiple copies of a product such as digital media or software.

The term clone is derived from the Greek word for "trunk branch" referring to the process whereby a new plant can be created from a twig. In horticulture the spelling clon was used until the twentieth century; the final e came into use to indicate the vowel is a "long o" instead of a "short o".12 Since the term entered the popular lexicon in a more general context the spelling clone has been used exclusively. Contents 1 Molecular cloning 2 Cellular cloning 2.1 Unicellular organisms 2.2 Cloning in stem cell research 3 Organism cloning 3.1 Horticultural 3.2 Parthenogenesis 3.3 Artificial cloning of organisms 3.3.1 Methods 3.3.2 Dolly the Sheep 3.3.3 Water buffalo 3.3.4 Species cloned 3.3.5 Human cloning 3.3.6 Ethical issues of cloning 3.3.7 Cloning extinct and endangered species 4 In science fiction 5 See also 6 References 7 External links Molecular cloning Main article: Molecular cloning

Molecular cloning refers to the process of making multiple molecules. Cloning is commonly used to amplify DNA fragments containing whole genes but it can also be used to amplify any DNA sequence such as promoters non-coding sequences and randomly fragmented DNA. It is used in a wide array of biological experiments and practical applications ranging from genetic fingerprinting to large scale protein production. Occasionally the term cloning is misleadingly used to refer to the identification of the chromosomal location of a gene associated with a particular phenotype of interest such as in positional cloning. In practice localization of the gene to a chromosome or genomic region does not necessarily enable one to isolate or amplify the relevant genomic sequence. To amplify any DNA sequence in a living organism that sequence must be linked to an origin of replication which is a sequence of DNA capable of directing the propagation of itself and any linked sequence. However a number of other features are needed and a variety of specialised cloning vectors (small piece of DNA into which a foreign DNA fragment can be inserted) exist that allow protein expression tagging single stranded RNA and DNA production and a host of other manipulations.

Cloning of any DNA fragment essentially involves four steps3 fragmentation - breaking apart a strand of DNA ligation - gluing together pieces of DNA in a desired sequence transfection - inserting the newly formed pieces of DNA into cells screening/selection - selecting out the cells that were successfully transfected with the new DNA

Although these steps are invariable among cloning procedures a number of alternative routes can be selected these are summarized as a 'cloning strategy'.

Initially the DNA of interest needs to be isolated to provide a DNA segment of suitable size. Subsequently a ligation procedure is used where the amplified fragment is inserted into a vector (piece of DNA). The vector (which is frequently circular) is linearised using restriction enzymes and incubated with the fragment of interest under appropriate conditions with an enzyme called DNA ligase. Following ligation the vector with the insert of interest is transfected into cells. A number of alternative techniques are available such as chemical sensitivation of cells electroporation optical injection and biolistics. Finally the transfected cells are cultured. As the aforementioned procedures are of particularly low efficiency there is a need to identify the cells that have been successfully transfected with the vector construct containing the desired insertion sequence in the required orientation. Modern cloning vectors include selectable antibiotic resistance markers which allow only cells in which the vector has been transfected to grow. Additionally the cloning vectors may contain colour selection markers which provide blue/white screening (-factor complementation) on X-gal medium. Nevertheless these selection steps do not absolutely guarantee that the DNA insert is present in the cells obtained. Further investigation of the resulting colonies must be required to confirm that cloning was successful. This may be accomplished by means of PCR restriction fragment analysis and/or DNA sequencing. Cellular cloning Unicellular organisms Cloning cell-line colonies using cloning rings

Cloning a cell means to derive a population of cells from a single cell. In the case of unicellular organisms such as bacteria and yeast this process is remarkably simple and essentially only requires the inoculation of the appropriate medium. However in the case of cell cultures from multi-cellular organisms cell cloning is an arduous task as these cells will not readily grow in standard media.

A useful tissue culture technique used to clone distinct lineages of cell lines involves the use of cloning rings (cylinders).4 According to this technique a single-cell suspension of cells that have been exposed to a mutagenic agent or drug used to drive selection is plated at high dilution to create isolated colonies; each arising from a single and potentially clonal distinct cell. At an early growth stage when colonies consist of only a few of cells sterile polystyrene rings (cloning rings) which have been dipped in grease are placed over an individual colony and a small amount of trypsin is added. Cloned cells are collected from inside the ring and transferred to a new vessel for further growth. Cloning in stem cell research Main article: Somatic cell nuclear transfer

Somatic cell nuclear transfer known as SCNT can also be used to create embryos for research or therapeutic purposes. The most likely purpose for this is to produce embryos for use in stem cell research. This process is also called "research cloning" or "therapeutic cloning." The goal is not to create cloned human beings (called "reproductive cloning") but rather to harvest stem cells that can be used to study human development and to potentially treat disease. While a clonal human blastocyst has been created stem cell lines are yet to be isolated from a clonal source.5 Organism cloning Further information: Asexual reproduction Organism cloning (also called reproductive cloning) refers to the procedure of creating a new multicellular organism genetically identical to another. In essence this form of cloning is an asexual method of reproduction where fertilization or inter-gamete contact does not take place. Asexual reproduction is a naturally occurring phenomenon in many species including most plants (see vegetative reproduction) and some insects. Scientists have made some major achievements with cloning including the asexual reproduction of sheep and cows. There is a lot of ethical debate over whether or not cloning should be used. However cloning or asexual propagation6 has been common practice in the horticultural world for hundreds of years. Horticultural The term clone is used in horticulture to refer to descendants of a single plant which were produced by vegetative reproduction or apomixis. Many horticultural plant cultivars are clones having been derived from a single individual multiplied by some process other than sexual reproduction. As an example some European cultivars of grapes represent clones that have been propagated for over two millennia. Other examples are potato and banana and grapes. Grafting can be regarded as cloning since all the shoots and branches coming from the graft are genetically a clone of a single individual but this particular kind of cloning has not come under ethical scrutiny and is generally treated as an entirely different kind of operation. Many trees shrubs vines ferns and other herbaceous perennials form clonal colonies. Parts of a large clonal colony often become detached from the parent termed fragmentation to form separate individuals. Some plants also form seeds asexually termed apomixis e.g. dandelion. Parthenogenesis Clonal derivation exists in nature in some animal species and is referred to as parthenogenesis (reproduction of an organism by itself without a mate). This is an asexual form of reproduction that is only found in females of some insects crustaceans and lizards. The growth and development occurs without fertilization by a male. In plants parthenogenesis means the development of an embryo from an unfertilized egg cell and is a component process of apomixis. In species that use the XY sex-determination system the offspring will always be female. An example is the "Little Fire Ant" (Wasmannia auropunctata) which is native to Central and South America but has spread throughout many tropical environments. Artificial cloning of organisms Artificial cloning of organisms may also be called reproductive cloning. Methods Reproductive cloning generally uses "somatic cell nuclear transfer" (SCNT) to create animals that are genetically identical. This process entails the transfer of a nucleus from a donor adult cell (somatic cell) to an egg that has no nucleus. If the egg begins to divide normally it is transferred into the uterus of the surrogate mother. Such clones are not strictly identical since the somatic cells may contain mutations in their nuclear DNA. Additionally the mitochondria in the cytoplasm also contains DNA and during SCNT this DNA is wholly from the donor egg thus the mitochondrial genome is not the same as that of the nucleus donor cell from which it was produced. This may have important implications for cross-species nuclear transfer in which nuclear-mitochondrial incompatibilities may lead to death. Artificial embryo splitting or embryo twinning may also be used as a method of cloning where an embryo is split in the maturation before embryo transfer. It is optimally performed at the 6- to 8-cell stage where it can be used as an expansion of IVF to increase the number of available embryos.7 If both embryos are successful it gives rise to monozygotic (identical) twins. Dolly the Sheep Main article: Dolly the Sheep Dolly a Finn-Dorset ewe was the first mammal to have been successfully cloned from an adult cell. She was cloned at the Roslin Institute in Scotland and lived there from her birth in 1996 until her death in 2003 when she was six. Her stuffed remains were placed at Edinburgh's Royal Museum part of the National Museums of Scotland.8 Dolly was publicly significant because the effort showed that the genetic material from a specific adult cell programmed to express only a distinct subset of its genes can be reprogrammed to grow an entirely new organism. Before this demonstration it had been shown by John Gurdon that nuclei from differentiated cells could give rise to an entire organism after transplantation into an enucleated egg.9 However this concept was not yet demonstrated in a mamallian system. Cloning Dolly the sheep had a low success rate per fertilized egg; she was born after 237 eggs were used to create 29 embryos which only produced three lambs at birth only one of which lived. Seventy calves have been created and one third of them died young; Prometea took 277 attempts. Notably although the first clones were frogs no adult cloned frog has yet been produced from a somatic adult nucleus donor cell. There were early claims that Dolly the Sheep had pathologies resembling accelerated aging. Scientists speculated that Dolly's death in 2003 was related to the shortening of telomeres DNA-protein complexes that protect the end of linear chromosomes. However other researchers including Ian Wilmut who led the team that successfully cloned Dolly argue that Dolly's early death due to respiratory infection was unrelated to deficiencies with the cloning process. Water buffalo On September 15 2007 the Philippines announced its development of Southeast Asias first cloned water buffalo. The Philippine Council for Agriculture Forestry and Natural Resources Research and Development (PCARRD) under the Department of Science and Technology in Los Baos Laguna approved this project.10 Species cloned Further information: List of animals that have been cloned The modern cloning techniques involving nuclear transfer have been successfully performed on several species. Landmark experimentsclarification needed in chronological order: Tadpole: (1952) Many scientists questioned whether cloning had actually occurred and unpublished experiments by other labs were not able to reproduce the reported results.citation needed Carp: (1963) In China embryologist Tong Dizhou produced the world's first cloned fish by inserting the DNA from a cell of a male carp into an egg from a female carp. He published the findings in a Chinese science journal.11 Mice: (1986) A mouse was the first mammal successfully cloned from an early embryonic cell. Soviet scientists Chaylakhyan Veprencev Sviridova and Nikitin had the mouse "Masha" cloned. Research was published in the magazine "Biofizika" volume II issue 5 of 1987.clarification needed12 Sheep: (1996) From early embryonic cells by Steen Willadsen. Megan and Morag13 cloned from differentiated embryonic cells in June 1995 and Dolly the sheep from a somatic cell in 1997.14 Rhesus Monkey: Tetra (January 2000) from embryo splitting15clarification needed16 Gaur: (2001) was the first endangered species cloned.17 Cattle: Alpha and Beta (males 2001) and (2005) Brazil18 Cat: CopyCat "CC" (female late 2001) Little Nicky 2004 was the first cat cloned for commercial reasons19 Dog: Snuppy a male Afghan hound was the first cloned dog (2005).20 Rat: Ralph the first cloned rat (2003)21 Mule: Idaho Gem a john mule born 4 May 2003 was the first horse-family clone.22 Horse: Prometea a Haflinger female born 28 May 2003 was the first horse clone.23 Water Buffalo: Samrupa was the first cloned water buffalo. It was born on February 6 2009 at India's Karnal National Diary Research Institute but died five days later due to lung infection.24 Pyrenean Ibex (2009) was the first extinct animal (extinct 2000) to be cloned back to life; the clone lived for seven minutes before dying of lung defects.25 Camel: (2009) Injaz is the first cloned camel.26 Human cloning Main article: Human cloning Human cloning is the creation of a genetically identical copy of an existing or previously existing human. The term is generally used to refer to artificial human cloning; human clones in the form of identical twins are commonplace with their cloning occurring during the natural process of reproduction. There are two commonly discussed types of human cloning: therapeutic cloning and reproductive cloning. Therapeutic cloning involves cloning adult cells for use in medicine and is an active area of research. Reproductive cloning would involve making cloned humans. A third type of cloning called replacement cloning is a theoretical possibility and would be a combination of therapeutic and reproductive cloning. Replacement cloning would entail the replacement of an extensively damaged failed or failing body through cloning followed by whole or partial brain transplant. The various forms of human cloning are controversial.27 There have been numerous demands for all progress in the human cloning field to be halted. Most scientific governmental and religious organizations oppose reproductive cloning. The American Association for the Advancement of Science (AAAS) and other scientific organizations have made public statements suggesting that human reproductive cloning be banned until safety issues are resolved.28 Serious ethical concerns have been raised by the future possibility of harvesting organs from clones.citation needed Some people have considered the idea of growing organs separately from a human organism - in doing this a new organ supply could be established without the moral implications of harvesting them from humans. Research is also being done on the idea of growing organs that are biologically acceptable to the human body inside of other organisms such as pigs or cows then transplanting them to humans a form of xenotransplantation. The first hybrid human clone was created in November 1998 by Advanced Cell Technologies.29 It was created from a man's leg cell and a cow's egg whose DNA was removed. It was destroyed after 12 days. Since a normal embryo implants at 14 days Dr Robert Lanza ACT's director of tissue engineering told the Daily Mail newspaper that the embryo could not be seen as a person before 14 days. While making an embryo which may have resulted in a complete human had it been allowed to come to term according to ACT: "ACT's aim was 'therapeutic cloning' not 'reproductive cloning'" On January 2008 Wood and Andrew French Stemagen's chief scientific officer in California announced that they successfully created the first 5 mature human embryos using DNA from adult skin cells aiming to provide a source of viable embryonic stem cells. Dr. Samuel Wood and a colleague donated skin cells and DNA from those cells was transferred to human eggs. It is not clear if the embryos produced would have been capable of further development but Dr. Wood stated that if that were possible using the technology for reproductive cloning would be both unethical and illegal. The 5 cloned embryos created in Stemagen Corporation lab in La Jolla were destroyed.30 Ethical issues of cloning Main article: Ethics of cloning Because of recent technological advancements the cloning of animals (and potentially humans) has been an issue. The Catholic Church and many religious organizations oppose all forms of cloningcitation needed on the grounds that life begins at conception. Judaism does not equate life with conception andcitation needed though some question the wisdom of cloning Orthodox rabbis generally find no firm reason in Jewish law and ethics to object to cloning.citation needed From the standpoint of classical liberalism concerns also exist regarding the protection of the identity of the individual and the right to protect one's genetic identity. Gregory Stock is a scientist and outspoken critic against restrictions on cloning research.31 Bioethicist Gregory Pence also attacks the idea of criminalizing attempts to clone humans.citation needed The social implications of an artificial human production scheme were famously explored in Aldous Huxley's novel Brave New World. On December 28 2006 the U.S. Food and Drug Administration (FDA) approved the consumption of meat and other products from cloned animals.32 Cloned-animal products were said to be virtually indistinguishable from the non-cloned animals. Furthermore companies would not be required to provide labels informing the consumer that the meat comes from a cloned animal.33 Critics have raised objections to the FDA's approval of cloned-animal products for human consumption arguing that the FDA's research was inadequate inappropriately limited and of questionable scientific validity.343536 Several consumer-advocate groups are working to encourage a tracking program that would allow consumers to become more aware of cloned-animal products within their food.37 Joseph Mendelson legal director of the Center for Food Safety said that cloned food still should be labeled since safety and ethical issues about it remain questionable. Carol Tucker Foreman director of food policy at the Consumer Federation of America stated that FDA does not consider the fact that the results of some studies revealed that cloned animals have increased rates of mortality and deformity at birth. Cloning extinct and endangered species Cloning or more precisely the reconstruction of functional DNA from extinct species has for decades been a dream of some scientists. The possible implications of this were dramatized in the best-selling novel by Michael Crichton and high budget Hollywood thriller Jurassic Park. In real life one of the most anticipated targets for cloning was once the Woolly Mammoth but attempts to extract DNA from frozen mammoths have been unsuccessful though a joint Russo-Japanese team is currently working toward this goal. And in January 2011 it was reported by Yomiuri Shimbun that a team of scientists headed by Akira Iritani of Kyoto University had built upon research by Dr. Wakayama saying that they will extract DNA from a mammoth carcass that had been preserved in a Russian laboratory and insert it into the egg cells of an African elephant in hopes of producing a mammoth embryo. The researchers said they hoped to produce a baby mammoth within six years.38 In 2001 a cow named Bessie gave birth to a cloned Asian gaur an endangered species but the calf died after two days. In 2003 a banteng was successfully cloned followed by three African wildcats from a thawed frozen embryo. These successes provided hope that similar techniques (using surrogate mothers of another species) might be used to clone extinct species. Anticipating this possibility tissue samples from the last bucardo (Pyrenean Ibex) were frozen in liquid nitrogen immediately after it died in 2000. Researchers are also considering cloning endangered species such as the giant panda ocelot and cheetah. The "Frozen Zoo" at the San Diego Zoo now stores frozen tissue from the world's rarest and most endangered species.3940 In 2002 geneticists at the Australian Museum announced that they had replicated DNA of the Thylacine (Tasmanian Tiger) extinct about 65 years previous using polymerase chain reaction.41 However on February 15 2005 the museum announced that it was stopping the project after tests showed the specimens' DNA had been too badly degraded by the (ethanol) preservative. On 15 May 2005 it was announced that the Thylacine project would be revived with new participation from researchers in New South Wales and Victoria. In January 2009 for the first time an extinct animal the Pyrenean ibex mentioned above was cloned at the Centre of Food Technology and Research of Aragon using the preserved DNA of the skin samples from 2001 and domestic goat egg-cells. (The ibex died shortly after birth due to physical defects in its lungs.) 42 One of the continuing obstacles in the attempt to clone extinct species is the need for nearly perfect DNA. Cloning from a single specimen could not create a viable breeding population in sexually reproducing animals. Furthermore even if males and females were to be cloned the question would remain open whether they would be viable at all in the absence of parents that could teach or show them their natural behavior. Cloning endangered species is a highly ideological issue. Many conservation biologists and environmentalists vehemently oppose cloning endangered speciesmainly because they think it may deter donations to help preserve natural habitat and wild animal populations. The "rule-of-thumb" in animal conservation is that if it is still feasible to conserve habitat and viable wild populations breeding in captivity should not be undertaken in isolation. In a 2006 review David Ehrenfeld concluded that cloning in animal conservation is an experimental technology that at its state in 2006 could not be expected to work except by pure chance and utterly failed a cost-benefit analysis.43 Furthermore he said it is likely to siphon funds from established and working projects and does not address any of the issues underlying animal extinction (such as habitat destruction hunting or other overexploitation and an impoverished gene pool). While cloning technologies are well-established and used on a regular basis in plant conservation care must be taken to ensure genetic diversity. He concluded: Vertebrate cloning poses little risk to the environment but it can consume scarce conservation resources and its chances of success in preserving species seem poor. To date the conservation benefits of transgenics and vertebrate cloning remain entirely theoretical but many of the risks are known and documented. Conservation biologists should devote their research and energies to the established methods of conservation none of which require transgenics or vertebrate cloning.43 In science fiction Cloning has been used in countless science fiction works throughout the years. Human cloning is usually the most popular kind that is used in these particular works mainly due to fact that it brings up controversial questions of identity.44 For example in C.J. Cherryhs novel Cyteen and in Aldous Huxleys novel Brave New World human cloning is a major plot device that not only drives the story along but also makes the reader think critically about what identity means. See also The President's Council on Bioethics References "Torrey Botanical Club: Volumes 42-45". Torreya Volumes 42-45 (Torrey Botanical Club): 133. 1942  American Association for the Advancement of Science (1903). Science. Moses King. pp. 502. http://books.google.com/booksidMIACAAAAYAAJ&pgPA502. Retrieved 8 October 2010.  Peter J. Russel (2005). iGenetics: A Molecular Approach. San Francisco California United States of America: Pearson Education. ISBN 0-8053-4665-1.  McFarland Douglas (2000). "Preparation of pure cell cultures by cloning". Methods in Cell Science 22 (1): 6366. doi:10.1023/A:1009838416621. PMID 10650336.  Gil Gideon (2008-01-17). "California biotech says it cloned a human embryo but no stem cells produced". Boston Globe. http://www.boston.com/news/health/blog/2008/01/californiabiot.html.  "Asexual Propagation". Aggie-horticulture.tamu.edu. http://aggie-horticulture.tamu.edu/plantanswers/misc/asexualpropagation.html. Retrieved 2010-08-04.  Illmensee K Levanduski M Vidali A Husami N Goudas VT (February 2009). "Human embryo twinning with applications in reproductive medicine". Fertil. Steril. 93 (2): 4237. doi:10.1016/j.fertnstert.2008.12.098. PMID 19217091.  TV documentary Visions Of The Future part 2 shows this process explores the social implicatins of cloning and contains footage of monoculture in livestock USA (2010-07-06). "PubMed home". Ncbi.nlm.nih.gov. http://www.ncbi.nlm.nih.gov/sites/entrez. Retrieved 2010-08-04.  Manila Times RP to produce Southeast Asias first cloned buffalo "Bloodlines timeline". PBS.org. http://www.pbs.org/bloodlines/timeline/texttimeline.html.  " ". Archived from the original on 2004-12-23. http://web.archive.org/web/20041223221951/http://www.whoiswho.ru/russian/Curnom/22003/cl.htm.  (Russian) "Gene Genie BBC World Service". Bbc.co.uk. 2000-05-01. http://www.bbc.co.uk/worldservice/scitech/highlights/wilmutt.shtml. Retrieved 2010-08-04.  McLaren A (2000). "Cloning: pathways to a pluripotent future". Science 288 (5472): 177580. doi:10.1126/science.288.5472.1775. PMID 10877698.  CNN. Researchers clone monkey by splitting embryo 2000-01-13. Retrieved 2008-08-05. By Dean Irvine (2007-11-19). "You again: Are we getting closer to cloning humans - CNN.com". Edition.cnn.com. http://edition.cnn.com/2007/WORLD/europe/11/16/ww.humancloning/index.htmlirefallsearch. Retrieved 2010-08-04.  "First cloned endangered species dies 2 days after birth". CNN. January 12 2001. http://archives.cnn.com/2001/NATURE/01/12/cloned.gaur/index.html. Retrieved April 30 2010.  Camacho Keite. Embrapa clona raa de boi ameaada de extino. Agncia Brasil. 2005-05-20. (Portuguese) Retrieved 2008-08-05 "Americas Pet kitten cloned for Christmas". BBC News. 2004-12-23. http://news.bbc.co.uk/1/hi/world/americas/4120179.stm. Retrieved 2010-08-04.  "First Dog Clone". News.nationalgeographic.com. http://news.nationalgeographic.com/news/2005/08/photogalleries/dogclone/. Retrieved 2010-08-04.  "Rat called Ralph is latest clone". BBC News. September 25 2003. http://news.bbc.co.uk/2/hi/science/nature/3136776.stm. Retrieved April 30 2010.  Associated Press August 25 2009 (2009-08-25). "Gordon Woods dies at 57; Veterinary scientist helped create first cloned mule". latimes.com. http://www.latimes.com/news/nationworld/nation/la-me-gordon-woods25-2009aug2505372986.story. Retrieved 2010-08-04.  "World's first cloned horse is born - 06 August 2003". New Scientist. http://www.newscientist.com/article/dn4026-worlds-first-cloned-horse-is-born.html. Retrieved 2010-08-04.  Kounteya Sinha TNN Feb 13 2009 12.33am IST (2009-02-13). "India clones world's first buffalo - India - The Times of India". Timesofindia.indiatimes.com. http://timesofindia.indiatimes.com/India-clones-worlds-first-buffalo/articleshow/4120044.cms. Retrieved 2010-08-04.  Extinct ibex is resurrected by cloning The Daily Telegraph January 31 2009 Spencer Richard (April 14 2009). "World's first cloned camel unveiled in Dubai". London: Telegraph.co.uk. http://www.telegraph.co.uk/news/newstopics/howaboutthat/5153780/Worlds-first-cloned-camel-unveiled-in-Dubai.html. Retrieved April 15 2009.  Pence Gregory E. (1998). Whos Afraid of Human Cloning. Rowman & Littlefield. paperback ISBN 0-8476-8782-1 and hardcover ISBN 0-8476-8781-3.  "AAAS Statement on Human Cloning". http://www.aaas.org/spp/sfrl/docs/cloningstatement.shtml.  "Details of hybrid clone revealed". BBC News. June 18 1999. http://news.bbc.co.uk/2/hi/science/nature/371378.stm. Retrieved April 30 2010.  Mature Human Embryos Created From Adult Skin Cells Washingtonpost.com New Page 0 "FDA says cloned animals are OK to eat - Health - More health news - msnbc.com". MSNBC. 2006-12-28. http://www.msnbc.msn.com/id/16372490. Retrieved 2010-08-04.  Meat of Cloned Food is Safe to Eat FDA Says "An HSUS Report: Welfare Issues with Genetic Engineering and Cloning of Farm Animals The Humane Society of the United States". Hsus.org. http://www.hsus.org/farm/resources/research/practices/geneticengineeringandcloningfarmanimals.html. Retrieved 2010-08-04.  "Not ready for prime time". Center for Food Safety. 21 march 2007. http://www.centerforfoodsafety.org/pubs/FINALFORMATTEDprime%20time.pdf. Retrieved 26 August 2010.  Michael Hansen Ph.D. (27 April 2007). "Comments of Consumers Union to US Food and Drug Administration on Docket No. 2003N-0573 Draft Animal Cloning Risk Assessment". Consumersunion.org. http://www.consumersunion.org/pdf/FDAclonecomments.pdf. Retrieved 26 August 2010.  "". Convio.net. https://secure3.convio.net/cfs/site/Advocacycmddisplay&pageUserAction&id302.  "Scientists 'to clone mammoth'". BBC News. 2003-08-18. http://news.bbc.co.uk/2/hi/asia-pacific/3075381.stm.  Heidi B. Perlman (2000-10-08). "Scientists Close on Extinct Cloning". The Washington Post. Associated Press. http://www.washingtonpost.com/wp-srv/aponline/20001008/aponline171938000.htm.  Pence Gregory E. (2005). Cloning After Dolly: Who's Still Afraid. Rowman & Littlefield. ISBN 0-7425-3408-1.  Holloway Grant (2002-05-28). "Cloning to revive extinct species". CNN.com. http://www.cnn.com/2002/WORLD/asiapcf/auspac/05/28/aust.thylacines/.  Gray Richard; Dobson Roger (31 January 2009). "Extinct ibex is resurrected by cloning". The Telegraph (London). http://www.telegraph.co.uk/scienceandtechnology/science/sciencenews/4409958/Extinct-ibex-is-resurrected-by-cloning.html. Retrieved 2009-02-01. dead link a b Ehrenfeld David (2006). "Transgenics and Vertebrate Cloning as Tools for Species Conservation". Conservation Biology 20 (3): 723732. doi:10.1111/j.1523-1739.2006.00399.x. PMID 16909565.  Yvonne A. De La Cruz Science Fiction Storytelling and Identity: Seeing the Human Through Android Eyes External links Cloning Fact Sheet from Human Genome Project Information website. 'Cloning' Freeview video by the Vega Science Trust and the BBC/OU The Reproductive Cloning Network. Cloning articles resources and links Cloning in Focus an accessible and comprehensive look at cloning research from the University of Utah's Genetic Science Learning Center Click and Clone. Try it yourself in the virtual mouse cloning laboratory from the University of Utah's Genetic Science Learning Center Cloning timeline: from CNN "Cloning Addendum: A statement on the cloning report issues by the President's Council on Bioethics" The National Review July 15 2002 8:45am Cloning educational resources and news from LiveScience.com Ian Wilmut to quit cloning game