Cloning

Cloning

The sea anemone (Anthopleura elegantissima) undergoing cloning

In biology, cloning is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as digital media or software.

The term clone is derived from the Ancient Greek word κλών klōn, "twig", 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".[1][2] Since the term entered the popular lexicon in a more general context, the spelling clone has been used exclusively.

In botany, the term lusus was traditionally used.[3]:21, 43

In the United States, the human consumption of meat and other products from cloned animals was approved by the

  • Cloning entry in the Internet Encyclopedia of Philosophy
  • Cloning Fact Sheet from Human Genome Project Information website.
  • 'Cloning' Freeview video by the Vega Science Trust and the BBC/OU
  • 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 Addendum: A statement on the cloning report issues by the President's Council on Bioethics," The National Review, July 15, 2002 8:45am

External links

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  3. ^ de Candolle, A. (1868). Laws of Botanical Nomenclature adopted by the International Botanical Congress held at Paris in August 1867; together with an Historical Introduction and Commentary by Alphonse de Candolle, Translated from the French. translated by H.A. Weddell. London: L. Reeve and Co. 
  4. ^ a b Walker, S. C. (2007). "Comparison of meat composition from offspring of cloned and conventionally produced boars". Theriogenology 67 (1): 178–184.  
  5. ^ a b Shinya Watanabe. Effect of calf death loss on cloned cattle herd derived from somatic cell nuclear transfer: Clones with congenital defects would be removed by the death loss. Animal Science Journal (September 2013), 84 (9), pg. 631-638 PMID 23829575
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  7. ^ Gil, Gideon (2008-01-17). "California biotech says it cloned a human embryo, but no stem cells produced". Boston Globe. 
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  12. ^ "Asexual Propagation". Aggie-horticulture.tamu.edu. Retrieved 2010-08-04. 
  13. ^ Sagers, Larry A. (2 March 2009) Proliferate favorite trees by grafting, cloning Utah Stae University, Deseret News (Salt Lake City) Retrieved 21 February 2014
  14. ^ Perrier, X.; De Langhe, E.; Donohue, M.; Lentfer, C.; Vrydaghs, L.; Bakry, F.; Carreel, F.; Hippolyte, I.; Horry, J. -P.; Jenny, C.; Lebot, V.; Risterucci, A. -M.; Tomekpe, K.; Doutrelepont, H.; Ball, T.; Manwaring, J.; De Maret, P.; Denham, T. (2011). spp.) domestication"Musa"Multidisciplinary perspectives on banana (. Proceedings of the National Academy of Sciences 108 (28): 11311.  
  15. ^ Castagnone-Sereno P, et al. Diversity and evolution of root-knot nematodes, genus Meloidogyne: new insights from the genomic era Annu Rev Phytopathol. 2013;51:203-20
  16. ^ a b Shubin, Neil (24 February 2008) Birds Do It. Bees Do It. Dragons Don’t Need To New York Times, Retrieved 21 February 2014
  17. ^ Explanation of the Spemann-Mangold experiment from a Nature Reviews article http://www.nature.com/nrm/journal/v7/n4/box/nrm1855_BX1.html
  18. ^ "Cloning Fact Sheet". Human Genome Project Information. Archived from the original on May 2, 2013. Retrieved 25 October 2011. 
  19. ^ Illmensee K, Levanduski M, Vidali A, Husami N, Goudas VT (February 2009). "Human embryo twinning with applications in reproductive medicine". Fertil. Steril. 93 (2): 423–7.  
  20. ^ Rantala, Milgram, M., Arthur (1999). Cloning: For and Against. Chicago, Illinois: Carus Publishing Company. p. 1.  
  21. ^ a b Swedin, Eric. "Cloning". CredoReference. Retrieved 23 September 2013. 
  22. ^ Lassen, J., Gjerris, M., & Sandøe, P. (2005). After Dolly—Ethical limits to the use of biotechnology on farm animals. Elsevier, 65, 992-1004.
  23. ^ TV documentary Visions Of The Future part 2 shows this process, explores the social implicatins of cloning and contains footage of monoculture in livestock
  24. ^ Gurdon J (Apr 1962). "Adult frogs derived from the nuclei of single somatic cells". Dev Biol. 4: 256–73.  
  25. ^ a b c Wakayama S1, Kohda T, Obokata H, Tokoro M, Li C, Terashita Y, Mizutani E, Nguyen VT, Kishigami S, Ishino F, Wakayama T (7 Mar 2013). "Successful serial recloning in the mouse over multiple generations". Cell Stem Cell. 12 (3): 293–7.  
  26. ^ BBC. February 22, 2008. BBC On This Day: 1997: Dolly the sheep is cloned
  27. ^ http://library.thinkquest.org/24355/data/details/1952.html
  28. ^ "Robert W. Briggs". National Academies Press. Retrieved December 1, 2012. 
  29. ^ "Bloodlines timeline". PBS.org. 
  30. ^ "Кто изобрел клонирование?". Archived from the original on 2004-12-23.  (Russian)
  31. ^ "Gene Genie | BBC World Service". Bbc.co.uk. 2000-05-01. Retrieved 2010-08-04. 
  32. ^ McLaren A (2000). "Cloning: pathways to a pluripotent future". Science 288 (5472): 1775–80.  
  33. ^ CNN. Researchers clone monkey by splitting embryo 2000-01-13. Retrieved 2008-08-05.
  34. ^ By Dean Irvine (2007-11-19). "You, again: Are we getting closer to cloning humans? - CNN.com". Edition.cnn.com. Retrieved 2010-08-04. 
  35. ^ Grisham, Julie (April 2000). "Pigs cloned for first time". Nature Biotechnology 18 (4): 365.  
  36. ^ Shukman, David (14 January 2014) China cloning on an 'industrial scale' BBC News Science and Environment, Retrieved 14 January 2014
  37. ^ "First cloned endangered species dies 2 days after birth". CNN. January 12, 2001. Retrieved April 30, 2010. 
  38. ^ Camacho, Keite. Embrapa clona raça de boi ameaçada de extinção. Agência Brasil. 2005-05-20. (Portuguese) Retrieved 2008-08-05
  39. ^ "Americas | Pet kitten cloned for Christmas". BBC News. 2004-12-23. Retrieved 2010-08-04. 
  40. ^ "Rat called Ralph is latest clone". BBC News. September 25, 2003. Retrieved April 30, 2010. 
  41. ^ Associated Press August 25, 2009 (2009-08-25). "Gordon Woods dies at 57; Veterinary scientist helped create first cloned mule". latimes.com. Retrieved 2010-08-04. 
  42. ^ "World's first cloned horse is born - 06 August 2003". New Scientist. Retrieved 2010-08-04. 
  43. ^ "First Dog Clone". News.nationalgeographic.com. Retrieved 2010-08-04. 
  44. ^ "World’s first cloned wolf dies". Retrieved 13 January 2013. 
  45. ^ Kounteya Sinha, TNN, Feb 13, 2009, 12.33am IST (2009-02-13). "India clones world's first buffalo - India - The Times of India". The Times of India. Retrieved 2010-08-04. 
  46. ^ Note: The Pyrenean ibex is an extinct sub-species; the broader species, the Spanish ibex, is thriving. Peter Maas. Pyrenean Ibex - Capra pyrenaica pyrenaica at the The Sixth Extinction]. Last updated April 15, 2012.
  47. ^ Extinct ibex is resurrected by cloning, The Daily Telegraph, January 31, 2009
  48. ^ Spencer, Richard (April 14, 2009). "World's first cloned camel unveiled in Dubai". London:  
  49. ^ Ishfaq-ul-Hassan (Mar 15, 2012). "India gets its second cloned animal Noorie, a pashmina goat". Kashmir, India: DNA. 
  50. ^ a b Kfoury C. Therapeutic cloning: promises and issues. Mcgill J Med. 2007 Jul;10(2):112-20. PMID 18523539
  51. ^ "Cloning Fact Sheet". U.S. Department of Energy Genome Program. 2009-05-11. Archived from the original on 2013-05-02. 
  52. ^ de Grey, Aubrey; Rae, Michael (September 2007). Ending Aging: The Rejuvenation Breakthroughs that Could Reverse Human Aging in Our Lifetime. New York, NY: St. Martin's Press, 416 pp. ISBN 0-312-36706-6.
  53. ^ Staff, Times Higher Education. August 10, 2001 In the news: Antinori and Zavos
  54. ^ "AAAS Statement on Human Cloning". 
  55. ^ McGee, G. (October 2011). "Primer on Ethics and Human Cloning". American Institute of Biological Sciences. 
  56. ^ "Universal Declaration on the Human Genome and Human Rights". UNESCO. 1997-11-11. Retrieved 2008-02-27. 
  57. ^ McGee, Glenn (2000). 'The Perfect Baby: Parenthood in the New World of Cloning and Genetics.' Lanham: Rowman & Littlefield.
  58. ^ Havstad, Joyce. "Human Reproductive Cloning: A Conflict of Liberties". San Diego State University. Blackwell Publishing Limited. 
  59. ^ Bob Sullivan, Technology correspondent for MSNBC. November 262003 Religions reveal little consensus on cloning - Health - Special Reports - Beyond Dolly: Human Cloning
  60. ^ William Sims Bainbridge, Ph.D. Religious Opposition to Cloning Journal of Evolution and Technology - Vol. 13 - October 2003
  61. ^ Staff, Humane Society Cloning
  62. ^ Sean Poulter for the Daily Mail. November 26, 2010. Clone farming would introduce cruelty on a massive scale, say animal welfare groups
  63. ^ "FDA says cloned animals are OK to eat".  
  64. ^ "An HSUS Report: Welfare Issues with Genetic Engineering and Cloning of Farm Animals".  
  65. ^ "Not Ready for Prime Time: FDA's Flawed Approach to Assessing the Safety of Food from Animal Clones".  (PDF)
  66. ^ Hansen, Michael (2007-04-27). "Comments of Consumers Union to US Food and Drug Administration on Docket No. 2003N-0573, Draft Animal Cloning Risk Assessment".  
  67. ^ a b Holt, W. V., Pickard, A. R., & Prather, R. S. (2004) Wildlife conservation and reproductive cloning. Reproduction, 126.
  68. ^  
  69. ^ Ono T, Li C, Mizutani E, Terashita Y, Yamagata K, Wakayama T (Dec 2010). "Inhibition of class IIb histone deacetylase significantly improves cloning efficiency in mice". Biol Reprod. 83 (6): 929–37.  
  70. ^ Ferris Jabr for Scientific American. March 11, 2013. Will cloning ever saved endangered species?
  71. ^ Heidi B. Perlman (2000-10-08). "Scientists Close on Extinct Cloning". The Washington Post. Associated Press. 
  72. ^  
  73. ^ Holloway, Grant (2002-05-28). "Cloning to revive extinct species". CNN.com. 
  74. ^ Gray, Richard; Dobson, Roger (31 January 2009). "Extinct ibex is resurrected by cloning". The Telegraph (London). Retrieved 2009-02-01. 
  75. ^ "'"Scientists 'to clone mammoth. BBC News. 2003-08-18. 
  76. ^ "BBC News". Bbc.co.uk. 2011-12-07. Retrieved 2012-08-19. 
  77. ^ Yong, Ed (2013-03-15). "Resurrecting the Extinct Frog with a Stomach for a Womb".  
  78. ^ "Long Now Foundation, Revive and Restore Project". 
  79. ^ "Generations of Cloned Mice With Normal Lifespans Created: 25th Generation and Counting". Science Daily. 7 March 2013. Retrieved 8 March 2013. 
  80. ^ Sleeper on IMDB
  81. ^ Hopkins, Patrick. "How Popular media represent cloning as an ethical problem". The Hastings Center.  
  82. ^ "Yvonne A. De La Cruz ''Science Fiction Storytelling and Identity: Seeing the Human Through Android Eyes''" (PDF). Retrieved 2012-08-19. 
  83. ^ "Uma Thurman, Rhys Ifans and Tom Wilkinson star in two plays for BBC Two" (Press release). BBC. 2008-06-19. Retrieved 2008-09-09. 
  84. ^ "A Number". BBC Two Listings. BBC. Retrieved 2008-09-09. 
  85. ^ Never Let Me Go on IMDB
  86. ^ The Island on IMDB
  87. ^ Star Wars: The Clone Wars on IMDB
  88. ^ Moon on IMDB
  89. ^ Could the Human Clones of 'Cloud Atlas' Be in Our Future?
  90. ^ The Boys from Brazil on IMDB
  91. ^ "Review of Bunshin". 
  92. ^ Orphan Black on IMDB

References

See also

In the 2013 television show Orphan Black,[92] cloning is used as a scientific study on the behavioral adaptation of the clones.

Cloning is also featured in the Halo franchise, particularly a technique known as "flash cloning" in which the unstable clone of an individual is created in an incredibly short span of time. Flash cloning is used by the UNSC to kidnap young children for induction into the SPARTAN-II military program, who are surreptitiously replaced by flash clones which die within a short span of time to ensure that no one looks for the children. The MMORPG EVE Online and online FPS DUST 514 takes place in the distant future where the player characters are all clones; at the moment of death, the person's brain-state is mapped, transmitted and applied to a 'blank' clone in a station or facility some distance away.

In 2012, a Japanese television show named "Bunshin" was created. The story's main character, Mariko, is a woman studying child welfare in Hokkaido. She grew up always doubtful about the love from her mother, who looked nothing like her and who died nine years before. One day, she finds some of her mother's belongings at a relative's house, and heads to Tokyo to seek out the truth behind her birth. She later discovered that she was a clone.[91]

In the anime A Certain Scientific Railgun, Level 5 esper Mikoto Misaka was cloned commercially over 20,000 times for the purposes of research into the possibility of a "Level 6" esper. In another anime/manga series Neon Genesis Evangelion, human cloning is a topic which features heavily around the origin of the character Ayanami Rei.

Cloning has been used in fiction as a way of recreating historical figures. In the 1976 Ira Levin novel The Boys from Brazil and its 1978 film adaptation,[90] Josef Mengele uses cloning to create copies of Adolf Hitler. A Parade of Mirrors and Reflections, a novel by Anatoly Kudryavitsky, centers on the cloning of deceased Soviet premier Yuri Andropov.

In the comedy film Multiplicity, a man clones himself three times with the help of a geneticist.

The exploitation of human clones for dangerous and undesirable work was examined in the 2009 British science fiction film Moon.[88] In the futuristic novel Cloud Atlas and subsequent film, one of the story lines focuses on a genetically-engineered Fabricant Clone named Sonmi~451 who is one of millions raised in an artificial "wombtank," destined to serve from birth. She is one of thousands of clones created for manual and emotional labor; Sonmi herself works as a server in a restaurant. She later discovers that the sole source of food for clones, called 'Soap', is manufactured from the clones themselves.[89]

The use of human cloning for military purposes has also been explored in several works. Star Wars portrays human cloning in Clone Wars,[87] Star Wars Episode II: Attack of the Clones and Star Wars Episode III: Revenge of the Sith, in the form of the Grand Army of the Republic, an army of cloned soldiers. The Expanded Universe also has numerous examples of cloning, including the Thrawn trilogy, The Hand of Thrawn duology, and Clone Wars-era media.

A recurring sub-theme of cloning fiction is the use of clones as a supply of

Science fiction has used cloning, most commonly and specifically human cloning, due to the fact that it brings up controversial questions of identity.[81][82] In Margaret Peterson Haddix's novel Double Identity, the main character discovers that she is a clone of her deceased older sister. A Number is a 2002 play by English playwright Caryl Churchill which addresses the subject of human cloning and identity, especially nature and nurture. The story, set in the near future, is structured around the conflict between a father (Salter) and his sons (Bernard 1, Bernard 2, and Michael Black) – two of whom are clones of the first one. A Number was adapted by Caryl Churchill for television, in a co-production between the BBC and HBO Films.[83] Starring Rhys Ifans and Tom Wilkinson, it was broadcast on BBC Two on 10 Sep 2008.[84]

Cloning is a recurring theme in a wide variety of contemporary science fiction, ranging from action films such as Jurassic Park (1993), The 6th Day (2000), Resident Evil (2002) and The Island (2005), to comedies such as Woody Allen's 1973 film Sleeper.[80]

In an article in the November 8, 1993 article of Time, cloning was portrayed in a negative way, modifying Michelangelo's Creation of Adam to depict Adam with five identical hands. Newsweek's March 10, 1997 issue also critiqued the ethics of human cloning, and included a graphic depicting identical babies in beakers.

In popular culture

After an eight-year project involving the use of a pioneering cloning technique, Japanese researchers created 25 generations of healthy cloned mice with normal lifespans, demonstrating that clones are not intrinsically shorter-lived than naturally born animals.[25][79]

Lifespan

Many such "de-extinction" projects are described in the Long Now Foundation's Revive and Restore Project.[78]

Scientists at the University of Newcastle and University of New South Wales announced in March 2013 that the very recently extinct gastric-brooding frog would be the subject of a cloning attempt to resurrect the species.[77]

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. 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.[75][76]

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 frozen cell nucleus of the skin samples from 2001 and domestic goat egg-cells. The ibex died shortly after birth due to physical defects in its lungs.[74]

In 2002, geneticists at the Australian Museum announced that they had replicated DNA of the Thylacine (Tasmanian Tiger), at the time extinct for about 65 years, using polymerase chain reaction.[73] 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 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 and cheetah.

Cloning, or more precisely, the reconstruction of functional DNA from extinct species has, for decades, been a dream. Possible implications of this were dramatized in the 1984 novel Carnosaur and the 1990 novel Jurassic Park. Hopes to save endangered and extinct species through cloning have seen slow but steady progress so far.[67][68] The best current cloning techniques have an average success rate of 9.4 percent[69] (and as high as 25 percent[25]) when working with familiar species such as mice, while cloning wild animals is usually less than 1 percent successful.[70] Several tissue banks have come into existence, including the "Frozen Zoo" at the San Diego Zoo, to store frozen tissue from the world's rarest and most endangered species.[67][71][72]

Cloning extinct and endangered species

Cloning of animals is opposed by animal-groups due to the number of cloned animals that suffer from malformations before they die,[61][62] and while food from cloned animals has been approved by the US FDA,[5][63] its use is opposed by groups concerned about food safety.[64][65][66]

Religious groups are divided, with some opposing the technology as usurping God's place and, to the extent embryos are used, destroying a human life; others support therapeutic cloning's potential life-saving benefits.[59][60]

Opponents of cloning have concerns that technology is not yet developed enough to be safe,[54] that it could be prone to abuse (leading to the generation of humans from whom organs and tissues would be harvested),[55][56] and have concerns about how cloned individuals could integrate with families and with society at large.[57][58]

Advocates support development of therapeutic cloning in order to generate tissues and whole organs to treat patients who otherwise cannot obtain transplants,[51] to avoid the need for immunosuppressive drugs,[50] and to stave off the effects of aging.[52] Advocates for reproductive cloning believe that parents who cannot otherwise procreate should have access to the technology.[53]

There are a variety of ethical positions regarding the possibilities of cloning, especially human cloning. While many of these views are religious in origin, the questions raised by cloning are faced by secular perspectives as well. Perspectives on human cloning are theoretical, as human therapeutic and reproductive cloning are not commercially used; animals are currently cloned in laboratories and in livestock production.

Ethical issues of cloning

Two commonly discussed types of theoretical human cloning are therapeutic cloning and reproductive cloning. Therapeutic cloning would involve cloning cells from a human for use in medicine and transplants, and is an active area of research, but is not in medical practice anywhere in the world, as of 2014. Two common methods of therapeutic cloning that are being researched are somatic-cell nuclear transfer and, more recently, pluripotent stem cell induction. Reproductive cloning would involve making an entire cloned human, instead of just specific cells or tissues.[50]

Human cloning is the creation of a genetically identical copy of a human. The term is generally used to refer to artificial human cloning, which is the reproduction of human cells and tissues. It does not refer to the natural conception and delivery of identical twins. The possibility of human cloning has raised controversies. These ethical concerns have prompted several nations to pass legislature regarding human cloning and its legality.

Human cloning

  • Tadpole: (1952) Robert Briggs and Thomas J. King had successfully cloned northern leopard frogs: thirty-five complete embryos and twenty-seven tadpoles from one-hundred and four successful nuclear transfers.[27][28]
  • 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.[29]
  • Mice: (1986) A mouse was 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 ХХХII, issue 5 of 1987.[30]
  • Sheep: Marked the first mammal being cloned (1984) from early embryonic cells by Steen Willadsen. Megan and Morag[31] cloned from differentiated embryonic cells in June 1995 and Dolly the sheep from a somatic cell in 1996.[32]
  • Rhesus Monkey: Tetra (January 2000) from embryo splitting[33] [34]
  • Pig: the first cloned pigs (March 2000).[35] By 2014, BGI in China was producing 500 cloned pigs a year to test new medicines.[36]
  • Gaur: (2001) was the first endangered species cloned.[37]
  • Cattle: Alpha and Beta (males, 2001) and (2005) Brazil[38]
  • Cat: CopyCat "CC" (female, late 2001), Little Nicky, 2004, was the first cat cloned for commercial reasons[39]
  • Rat: Ralph, the first cloned rat (2003)[40]
  • Mule: Idaho Gem, a john mule born 4 May 2003, was the first horse-family clone.[41]
  • Horse: Prometea, a Haflinger female born 28 May 2003, was the first horse clone.[42]
  • Dog: Snuppy, a male Afghan hound was the first cloned dog (2005).[43]
  • Wolf: Snuwolf and Snuwolffy, the first two cloned female wolves (2005).[44]
  • 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.[45]
  • Pyrenean Ibex (2009) was the first extinct animal to be cloned back to life; the clone lived for seven minutes before dying of lung defects.[46][47]
  • Camel: (2009) Injaz, is the first cloned camel.[48]
  • Pashmina goat: (2012) Noori, is the first cloned pashmina goat. Scientists at the faculty of veterinary sciences and animal husbandry of Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir successfully cloned the first Pashmina goat (Noori) using the advanced reproductive techniques under the leadership of Riaz Ahmad Shah.[49]

The modern cloning techniques involving nuclear transfer have been successfully performed on several species. Notable experiments include:

Species cloned

Dolly was named after performer Dolly Parton because the cells cloned to make her were from a mammary gland cell, and Parton is known for her ample cleavage.[26]

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. This idea that the nuclei have not irreversibly aged was shown in 2013 to be true for mice.[25]

The first mammalian cloning (resuliting in Dolly the sheep) had a success rate per 277 fertilized eggs of 29 embryos, which produced three lambs at birth, one of which lived. For a bovine experiment involving seventy cloned calves, one third of them died young. For horses, Prometea took 814 attempts. Notably, although the first clones were frogs, no adult cloned frog has yet been produced from a somatic adult nucleus donor cell.

Dolly was publicly significant because the effort showed that 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.[24] However, this concept was not yet demonstrated in a mammalian system.

Dolly, a Finn-Dorset ewe, was the first mammal to have been successfully cloned from an adult cell. Dolly was formed by taking a cell from the udder of her biological mother. Her biological mother was 6 years old when the cells were taken from her udder.[20] Dolly's embryo was created by taking the cell and inserting it into a sheep ovum. It took 434 attempts before an embryo was successful.[21] The embryo was then placed inside a female sheep that went through a normal pregnancy.[22] 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. She was born on July 5, 1996 but not announced to the world until February 22, 1997.[21] Her stuffed remains were placed at Edinburgh's Royal Museum, part of the National Museums of Scotland.[23]

Dolly clone

Dolly the sheep

Artificial embryo splitting or embryo twinning, a technique that creates monozygotic twins from a single embryo, is not considered in the same fashion as other methods of cloning. During that procedure, an donor embryo is split in two distinct embryos, that can then be transferred via 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.[19] If both embryos are successful, it gives rise to monozygotic (identical) twins.

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 from which the nucleus has been removed, or to a cell from a blastocyst from which the nucleus has been removed.[18] 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 mitochondrial DNA is wholly from the cytoplasmic donor's 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.

Methods

Hilde Mangold, were the first to perform somatic-cell nuclear transfer using amphibian embryos – one of the first moves towards cloning.[17]

First moves

Artificial cloning of organisms may also be called reproductive cloning.

Artificial cloning of organisms

but has spread throughout many tropical environments. South America and Central), which is native to Wasmannia auropunctata" (Fire Ant, the offspring will always be female. An example is the "Little XY sex-determination system. 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 lizards and [16]Komodo dragon), the [16]Hammerhead shark fish (for example the [15] Clonal derivation exists in nature in some animal species and is referred to as

Parthenogenesis

Many trees, shrubs, vines, ferns and other herbaceous perennials form clonal colonies naturally. Parts of an individual plant may become detached by fragmentation and grow on to become separate clonal individuals. A common example is in the vegetative reproduction of moss and liverwort gametophyte clones by means of gemmae. Some vascular plants e.g. dandelion and certain viviparous grasses also form seeds asexually, termed apomixis, resulting in clonal populations of genetically identical individuals.

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.[13] As an example, some European cultivars of grapes represent clones that have been propagated for over two millennia. Other examples are potato and banana.[14] 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.

Horticultural

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 propagation,[12] has been common practice in the horticultural world for hundreds of years.

Organism cloning

In SCNT, not all of the donor cell's genetic information is transferred, as the donor cell's mitochondria that contain their own mitochondrial DNA are left behind. The resulting hybrid cells retain those mitochondrial structures which originally belonged to the egg. As a consequence, clones such as Dolly that are born from SCNT are not perfect copies of the donor of the nucleus.

SCNT is seen as a good method for producing agriculture animals for food consumption. It successfully cloned sheep, cattle, goats, and pigs. Another benefit is SCNT is seen as a solution to clone endangered species that are on the verge of going extinct.[10] However, stresses placed on both the egg cell and the introduced nucleus are enormous, leading to a high loss in resulting cells. For example, the cloned sheep Dolly was born after 277 eggs were used for SCNT, which created 29 viable embryos. Only three of these embryos survived until birth, and only one survived to adulthood.[11] As the procedure currently cannot be automated, and has to be performed manually under a microscope, SCNT is very resource intensive. The biochemistry involved in reprogramming the differentiated somatic cell nucleus and activating the recipient egg is also far from being well-understood.

The process of cloning a particular farm animal using SCNT is relatively the same for all animals. The first step is to collect the somatic cells from the animal that will be cloned. The somatic cells could be used immediately or stored in the laboratory for later use.[10] The hardest part of SCNT is removing maternal DNA from an oocyte at metaphase II. Once this has been done, the somatic nucleus can be inserted into an egg cytoplasm.[10] This creates a one-cell embryo. The grouped somatic cell and egg cytoplasm are then introduced to an electrical current.[10] This energy will hopefully allow the cloned embryo to begin development. The successfully developed embryos are then placed in surrogate recipients, such as a cow or sheep in the case of farm animals.[10]

The reason why SCNT is used for cloning is because somatic cells can be easily acquired and cultured in the lab. This process can either add or delete specific genomes of farm animals. A key point to remember is that cloning is achieved when the oocyte maintains its normal functions and instead of using sperm and egg genomes to replicate, the oocyte is inserted into the donor’s somatic cell nucleus.[10] The oocyte will react on the somatic cell nucleus, the same way it would on sperm cells.[10]

Therapeutic cloning is achieved by creating embryonic stem cells in the hopes of treating diseases such as diabetes and Alzheimer’s. The process begins by removing the nucleus (containing the DNA) from an egg cell and inserting a nucleus from the adult cell to be cloned.[8] In the case of someone with Alzheimer’s disease, the nucleus from a skin cell of that patient is placed into an empty egg. The reprogrammed cell begins to develop into an embryo because the egg reacts with the transferred nucleus. The embryo will become genetically identical to the patient.[8] The embryo will then form a blastocyst which has the potential to form/become any cell in the body.[9]

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.[7]

Cloning stem cells

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 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 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.

Cloning cell-line colonies using cloning rings

Cloning unicellular organisms

Cell cloning

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 (alpha-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.

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

  1. fragmentation - breaking apart a strand of DNA
  2. ligation - gluing together pieces of DNA in a desired sequence
  3. transfection - inserting the newly formed pieces of DNA into cells
  4. screening/selection - selecting out the cells that were successfully transfected with the new DNA

Cloning of any DNA fragment essentially involves four steps[6]

Molecular cloning refers to the process of making multiple molecules. Cloning is commonly used to amplify 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.

Molecular cloning

Contents

  • Molecular cloning 1
  • Cell cloning 2
    • Cloning unicellular organisms 2.1
    • Cloning stem cells 2.2
  • Organism cloning 3
    • Horticultural 3.1
    • Parthenogenesis 3.2
    • Artificial cloning of organisms 3.3
      • First moves 3.3.1
      • Methods 3.3.2
      • Dolly the sheep 3.3.3
      • Species cloned 3.3.4
      • Human cloning 3.3.5
      • Ethical issues of cloning 3.3.6
      • Cloning extinct and endangered species 3.3.7
    • Lifespan 3.4
  • In popular culture 4
  • See also 5
  • References 6
  • External links 7

such as Europe, particularly over the labeling issue. [5] Such practice has met strong resistance in other regions due to misinformation,[4]