Usuario:Miguel.baillon/Articulo en Desarrollo 1

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Human cloning

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Diagram of the ways to reprogram cells along with the development of humans.

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 tissue, and is not in medical practice anywhere in the world. It does not refer to identical twins. The possibility of human cloning has raised controversies.

There are two commonly discussed types of theoretical human cloning: 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. 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.

History[editar]

Although the possibility of cloning humans had been the subject of speculation for much of the twentieth century, scientists and policy makers began to take the prospect seriously in the 1960s.

Nobel Prize winning geneticist Joshua Lederberg advocated cloning and genetic engineering in an article in The American Naturalist in 1966 and again, the following year, in The Washington Post.[1]​ He sparked a debate with conservative bioethicist Leon Kass, who wrote at the time that "the programmed reproduction of man will, in fact, dehumanize him." Another Nobel Laureate, James D. Watson, publicized the potential and the perils of cloning in his Atlantic Monthly essay, "Moving Toward the Clonal Man", in 1971.[2]​

With the cloning of a sheep known as Dolly in 1996 by somatic cell nuclear transfer (SCNT), the idea of human cloning became a hot debate topic.[3]​ Many nations outlawed it, while a few scientists promised to make a clone within the next few years. The first hybrid human clone was created in November 1998, by Advanced Cell Technology. It was created using SCNT - a nucleus was taken from a man's leg cell and inserted into a cow's egg from which the nucleus had been removed, and the hybrid cell was cultured, and developed into an embyro. The embryo was destroyed after 12 days.[4]​ Since a normal embryo implants at the fourteenth day, Robert Lanza, ACT's director of tissue engineering, told the Daily Mail newspaper that the embryo could not be seen as a person before the fourteenth day.[cita requerida]

In 2004 and 2005, Hwang Woo-suk, a professor at Seoul National University published two separate articles in the journal Science claiming to have successfully harvested pluripotent, embryonic stem-cells from a cloned human blastocyst using somatic-cell nuclear transfer techniques. Hwang claimed to have created 11 different patent-specific stem cell lines. This would have been the first major breakthrough in human cloning.[5]​ However, in 2006 Science retracted both of his articles on clear evidence that much of his data from the experiments was fabricated.[6]​

On January 2008, Dr. Samuel Wood and Andrew French of the biotechnology company Stemagen, announced that they successfully created the first 5 mature human embryos, aiming to provide a source of viable embryonic stem cells, using SCNT. In this case, each embryo was created by taking a nucleus from a skin cell (donated by Wood and a colleague) and inserted it into a human egg from which the nucleus had been removed. 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 were destroyed.[7]​[8]​

In 2013, a group of scientists led by Shoukhrat Mitalipov published a report of successful creation of embryos using SCNT.[9]​ A year later, a team led by Robert Lanza reported that they had replicated Mitalipov's results and further demonstrated the effectiveness by cloning adult cells.[3]​[10]​ The researchers took DNA from two donors – a 35-year-old man and a 75-year-old man – and electrically fused it into a normal human egg that had been stripped of its DNA.[11]​ The egg was stimulated and given caffeine to prevent early cell division. A total of 77 eggs from four donors were divided into two groups. Of the 38 with the 30 minute wait period used in previous experiments none developed, while two of the 39 with a two hour wait developed. The two successes came from the same egg donor, but with different DNA donors.[3]​

Methods[editar]

Somatic cell nuclear transfer (SCNT)[editar]

Diagram of SCNT Process
Artículo principal: Somatic cell nuclear transfer

In somatic cell nuclear transfer ("SCNT"), the nucleus of a somatic cell is taken from a donor and transplanted into a host egg cell, which had its own genetic material removed previously, making it an enucleated egg. After the donor somatic cell genetic material is transferred into the host oocyte with a micropipette, the somatic cell genetic material is fused with the egg using an electric current. Once the two cells have fused, the new cell can be permitted to grow in a surrogate or artificially.[12]​

Induced pluripotent stem cells (iPSCs)[editar]

Overview of iPS cells
Artículo principal: Induced pluripotent stem cell

Creating induced pluripotent stem cells ("iPSCs") is a long and inefficient process. Pluripotency refers to a stem cell that has the potential to differentiate into any of the three germ layers: endoderm (interior stomach lining, gastrointestinal tract, the lungs), mesoderm (muscle, bone, blood, urogenital), or ectoderm (epidermal tissues and nervous system).[13]​ A specific set of genes, often called "reprogramming factors", are introduced into a specific adult cell type. These factors send signals in the mature cell that cause the cell to become a pluripotent stem cell. This process is highly studied and new techniques are being discovered frequently on how to better this induction process.

Depending on the method used, reprogramming of adult cells into iPSCs for implantation could have severe limitations in humans. If a virus is used as a reprogramming factor for the cell, cancer-causing genes called oncogenes may be activated. These cells would appear as rapidly dividing cancer cells that do not respond to the body's natural cell signaling process. However, in 2008 scientists discovered a technique that could remove the presence of these oncogenes after pluripotency induction, thereby increasing the potential use of iPSC in humans.[14]​

Potential medical uses[editar]

Véase también: Personalized medicine
Stem cell treatments

With the available and developing technologies of iPSCs, as well as the progress in the Human Genome Project, hopes for more effective cures to disease are within reach. The traditional SCNT method of cloning cells has proven ineffective in humans. Therefore, researchers are shifting their focus toward developing iPSCs. The process of iPSC would allow for patient-specific stem cells, meaning that each person could have his or her own pluripotent cell line. This personalization of stem cells would avoid the risk of the cells being rejected by the individual's immune system.

Studies in animals have shown that iPSCs could potentially be used to treat diseases such as Parkinson's disease and diabetes as well as damage to the body such as spinal cord injury.[15]​ The potential to derive stem cells from clones genetically identical to patients shows great promise in the medical field. Human cloning could improve current stem cell therapy methods and provide patient-specific stem cells for more effective treatment, especially considering those cells are from the patient and not a donor. Most recent stem cell therapies rely on stem cells from umbilical cords and embryos.[16]​ Using stem cells derived from an individual's somatic cells would make stem cell therapy more effective, as well as available to more people — especially to those who do not preserve their cord blood.

Ethical implications[editar]

Artículo principal: Ethics of cloning

In bioethics, the ethics of cloning refers to a variety of ethical positions regarding the practice and 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.

Advocates support development of therapeutic cloning in order to generate tissues and whole organs to treat patients who otherwise cannot obtain transplants,[17]​ to avoid the need for immunosuppressive drugs,[18]​ and to stave off the effects of aging.[19]​ Advocates for reproductive cloning believe that parents who cannot otherwise procreate should have access to the technology.[20]​

Opponents of cloning have concerns that technology is not yet developed enough to be safe,[21]​ that it could be prone to abuse (leading to the generation of humans from whom organs and tissues would be harvested),[22]​[23]​ and have concerns about how cloned individuals could integrate with families and with society at large.[24]​[25]​

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.[26]​[27]​

Current law[editar]

Australia[editar]

Australia has prohibited human cloning,[28]​ though as of December 2006, a bill legalising therapeutic cloning and the creation of human embryos for stem cell research passed the House of Representatives. Within certain regulatory limits, and subject to the effect of state legislation, therapeutic cloning is now legal in some parts of Australia.[29]​

Canada[editar]

Canadian law prohibits the following: cloning humans, cloning stem cells, growing human embryos for research purposes, and buying or selling of embryos, sperm, eggs or other human reproductive material.[30]​ It also bans making changes to human DNA that would pass from one generation to the next, including use of animal DNA in humans. Surrogate mothers are legally allowed, as is donation of sperm or eggs for reproductive purposes. Human embryos and stem cells are also permitted to be donated for research.[cita requerida]

There have been consistent calls in Canada to ban human reproductive cloning since the 1993 Report of the Royal Commission on New Reproductive Technologies. Polls have indicated that an overwhelming majority of Canadians oppose human reproductive cloning, though the regulation of human cloning continues to be a significant national and international policy issue. The notion of "human dignity" is commonly used to justify cloning laws. The basis for this justification is that reproductive human cloning necessarily infringes notions of human dignity.[31]​[32]​[33]​[34]​

Denmark[editar]

Denmark has not currently agreed to any genetic laws or bans and does not appear to show any interest in banning human cloning and human transgenics.[cita requerida]

European Union[editar]

The European Convention on Human Rights and Biomedicine prohibits human cloning in one of its additional protocols, but this protocol has been ratified only by Greece, Spain and Portugal. The Charter of Fundamental Rights of the European Union explicitly prohibits reproductive human cloning. The charter is legally binding for the institutions of the European Union under the Treaty of Lisbon.[cita requerida]

India[editar]

India does not have specific law regarding cloning but has guidelines prohibiting whole human cloning or reproductive cloning. India allows theraputic cloning and the use of embryonic stem cells for research proposes.[35]​[36]​

Romania[editar]

Human cloning is prohibited in the Charter of Romania's Constitutional rights. It is viewed as a basic violation of a human's right to safety of identity, and personality.[cita requerida]

Serbia[editar]

Human cloning is explicitly prohibited in Article 24, "Right to Life" of the 2006 Constitution of Serbia.[37]​

United Kingdom[editar]

On January 14, 2001 the British government passed The Human Fertilisation and Embryology (Research Purposes) Regulations 2001[38]​ to amend the Human Fertilisation and Embryology Act 1990 by extending allowable reasons for embryo research to permit research around stem cells and cell nuclear replacement, thus allowing therapeutic cloning. However, on 15 November 2001, a pro-life group won a High Court legal challenge, which struck down the regulation and effectively left all forms of cloning unregulated in the UK. Their hope was that Parliament would fill this gap by passing prohibitive legislation.[39]​[40]​ Parliament was quick to pass the Human Reproductive Cloning Act 2001 which explicitly prohibited reproductive cloning. The remaining gap with regard to therapeutic cloning was closed when the appeals courts reversed the previous decision of the High Court.[41]​

The first licence was granted on August 11, 2004 to researchers at the University of Newcastle to allow them to investigate treatments for diabetes, Parkinson's disease and Alzheimer's disease.[42]​ The Human Fertilisation and Embryology Act 2008, a major review of fertility legislation, repealed the 2001 Cloning Act by making amendments of similar effect to the 1990 Act. The 2008 Act also allows experiments on hybrid human-animal embryos.[43]​

United Nations[editar]

On December 13, 2001, the United Nations General Assembly began elaborating an international convention against the reproductive cloning of humans. A broad coalition of States, including Spain, Italy, the Philippines, the United States, Costa Rica and the Holy See sought to extend the debate to ban all forms of human cloning, noting that, in their view, therapeutic human cloning violates human dignity. Costa Rica proposed the adoption of an international convention to ban all forms of human cloning. Unable to reach a consensus on a binding convention, in March 2005 a non-binding United Nations Declaration on Human Cloning, calling for the ban of all forms of Human Cloning contrary to human dignity, was adopted.[44]​[45]​

United States[editar]

In 1998, 2001, 2004, and 2007, the United States House of Representatives voted whether to ban all human cloning, both reproductive and therapeutic. Each time, divisions in the Senate over therapeutic cloning prevented either competing proposal (a ban on both forms or reproductive cloning only) from passing. On March 10, 2010 a bill (HR 4808) was introduced with a section banning federal funding for human cloning.[46]​ Such a law, if passed, would not prevent research from occurring in private institutions (such as universities) that have both private and federal funding. There are currently no federal laws in the United States which ban cloning completely, and any such laws would raise difficult Constitutional questions similar to the issues raised by abortion. Thirteen American states (Arkansas, California, Connecticut, Iowa, Indiana, Massachusetts, Maryland, Michigan, North Dakota, New Jersey, Rhode Island, South Dakota, and Virginia) ban reproductive cloning and three states (Arizona, Maryland, and Missouri) prohibit use of public funds for such activities.[47]​

In popular culture[editar]

Artículo principal: Cloning#In popular culture

Cloning is a recurring theme in a wide variety of contemporary science fiction. Aspects of cloning can be seen in action films such as The 6th Day, Resident Evil, The Island, and Jurassic Park. The theme of cloning can even be seen in comedies such as Woody Allen's 1973 film Sleeper.[48]​ Other movies have used the idea of cloning as a vehicle to explore issues of identity and human relationships.[49]​[50]​

References[editar]

  1. ↑ Joshua Lederberg. (1966). Experimental Genetics and Human Evolution. The American Naturalist 100, 915, pp. 519-531.
  2. ↑ Watson, James. "Moving Toward a Clonal Man: Is This What We Want?" The Atlantic Monthly (1971).
  3. ↑ a b c Alice Park (April 17, 2014). «Researchers Clone Cells From Two Adult Men». TIME. Consultado el April 18, 2014. 
  4. ↑ «Details of hybrid clone revealed». BBC News. June 18, 1999. Consultado el April 30, 2010. 
  5. ↑ Fischbak, Ruth L., John D. Loike, Janet Mindes, and Columbia Center for New Media Teaching & Learning. The Cloning Scandal of Hwang Woo-Suk, part of the online course, Stem Cells: Biology, Ethics, and Applications
  6. ↑ Kennedy, Donald. "Responding to Fraud." Science 314.5804 (2006): 1353. PMID 17138870
  7. ↑ Rick Weiss for the Washington Post January 18, 2008 Mature Human Embryos Created From Adult Skin Cells
  8. ↑ French AJ et al Development of human cloned blastocysts following somatic cell nuclear transfer with adult fibroblasts. Stem Cells. 2008 Feb;26(2):485-93. Epub 2008 Jan 17. PMID 18202077
  9. ↑ Tachibana, T et al. Human Embryonic Stem Cells Derived by Somatic Cell Nuclear Transfer Cell. 2013 Jun 6;153(6):1228-38. Epub 2013 May 15. PMID 23683578
  10. ↑ Chung YG et al Human Somatic Cell Nuclear Transfer Using Adult Cells Cell Stem Cell (2014), http://dx.doi.org/10.1016/j.stem.2014.03.015
  11. ↑ Sharon Begley (April 17, 2014). «In a cloning first, scientists create stem cells from adults». Reuters. Consultado el April 18, 2014. 
  12. ↑ Gilbert, Scott F. (30 de junio de 2013). Developmental Biology, 10th ed. Sinauer Associates, Inc. pp. 32-33. ISBN 9780878939787. 
  13. ↑ Binder, edited by Marc D.; Hirokawa, Nobutaka; (eds.), Uwe Windhorst (2009). Encyclopedia of neuroscience ([Online-Ausg.] edición). Berlin: Springer. ISBN 978-3540237358. 
  14. ↑ Kaplan, Karen (6 de marzo de 2009). «Cancer threat removed from stem cells, scientists say». Los Angeles Times. 
  15. ↑ Rose, Meghan. "Cloning Produces Human Embryonic Stem Cells." Science News Web Edition (2013): n. pag. AccessScience from McGraw-Hill Education. Society for Science & the Public, 26 May 2013. Web. 17 Mar. 2014.<http://www.accessscience.com/content/cloning-produces-human-embryonic-stem-cells/SN15431>.
  16. ↑ Singec I, Jandial R, Crain A, Nikkhah G, Snyder EY (2007). «The leading edge of stem cell therapeutics». Annu. Rev. Med. 58: 313-28. PMID 17100553. doi:10.1146/annurev.med.58.070605.115252. 
  17. ↑ «Cloning Fact Sheet». U.S. Department of Energy Genome Program. 11 de mayo de 2009. Archivado desde el original el 2 de mayo de 2013. 
  18. ↑ Por favor, pon la referencia que aparece aquí.
  19. ↑ de Grey, Michael; Rae (2007). Ending Aging: The Rejuvenation Breakthroughs that Could Reverse Human Aging in Our Lifetime. New York, NY: St. Martin's Press. ISBN 0-312-36706-6. 
  20. ↑ Staff, Times Higher Education. August 10, 2001 In the news: Antinori and Zavos
  21. ↑ «AAAS Statement on Human Cloning». 
  22. ↑ McGee, G. (October 2011). «Primer on Ethics and Human Cloning». American Institute of Biological Sciences. 
  23. ↑ «Universal Declaration on the Human Genome and Human Rights». UNESCO. 11 de noviembre de 1997. Consultado el 27 de febrero de 2008. 
  24. ↑ McGee, Glenn (2000). The Perfect Baby: Parenthood in the New World of Cloning and Genetics (2nd edición). Lanham: Rowman & Littlefield. ISBN 0-8476-9758-4. 
  25. ↑ Havstad, Joyce. «Human Reproductive Cloning: A Conflict of Liberties». San Diego State University. Blackwell Publishing Limited. 
  26. ↑ Bob Sullivan, Technology correspondent for MSNBC. November 262003 Religions reveal little consensus on cloning - Health - Special Reports - Beyond Dolly: Human Cloning
  27. ↑ William Sims Bainbridge, Ph.D. Religious Opposition to Cloning Journal of Evolution and Technology - Vol. 13 - October 2003
  28. ↑ Prohibition of Human Cloning for Reproduction Act 2002 National Health and Medical Research Council, 12 June 2007
  29. ↑ (April 2014) Research cloning - Legal Aspects Deutches Referenzzentrum fur Ethik in den Biowissenschaften, Retrieved 19 April 2014
  30. ↑ Philipkoski, Kristen (17 March 2004). «Canada Closes Door on Cloning». Wired. 
  31. ↑ "Overview of World Human Cloning Policies." Connexions - Sharing Knowledge and Building Communities. N.p., n.d. Web. 29 Nov. 2011. http://cnx.org/content/m14834/latest/
  32. ↑ "Canada Bans Human Cloning - Research and Read Books, Journals, Articles at Questia Online Library." Questia - The Online Library of Books and Journals. N.p., n.d. Web. 7 Dec. 2011. http://www.questia.com/googleScholar.qst?docId=5006805131.
  33. ↑ "Canada Closes Door on Cloning ." Wired.com . N.p., n.d. Web. 29 Nov. 2011. <http://www.wired.com/medtech/health/news/2004/03/62695>
  34. ↑ "Regulating and treating conception problems - Health - CBC News." CBC.ca - Canadian News Sports Entertainment Kids Docs Radio TV. N.p., n.d. Web. 7 Dec. 2011. http://www.cbc.ca/news/health/story/2009/02/05/f-reprotech.html.
  35. ↑ Bagla, Pallava (24 de junio de 2009). «Should India ban human cloning?». NDTV (New Delhi). Consultado el Apr 18, 2014. 
  36. ↑ «Cloning Ethical Policies on the Human Genome, Genetic Research and Services [India]». Genetics & Public Policy Center. 
  37. ↑ «Constitution of the Republic of Serbia, II Human and Minority Rights and Freedoms». Government of Serbia. Consultado el 15 de mayo de 2013. 
  38. ↑ Plantilla:UK-LEG
  39. ↑ SD Pattinson (2006), Medical Law and Ethics, Sweet & Maxwell, ISBN 978-0-421-88950-7 .
  40. ↑ «Campaigners win cloning challenge». London: BBC News. 15 November 2001. Consultado el 6 de septiembre de 2008. 
  41. ↑ «Lords uphold cloning law». BBC News Online (London). 13 March 2003. 
  42. ↑ «HFEA grants the first therapeutic cloning licence for research». HFEA. 11 August 2004. Consultado el 6 de septiembre de 2008. 
  43. ↑ «MPs support embryology proposals». BBC News Online (London). 23 October 2008. 
  44. ↑ "United Nations Declaration on Human Cloning". Bio Etica Web. March 16, 2005.
  45. ↑ «Ad Hoc Committee on an International Convention against the Reproductive Cloning of Human Beings». United Nations. 18 de mayo de 2005. Consultado el 28 de enero de 2007. 
  46. ↑ «H. R. 4808 Stem Cell Research Advancement Act of 2009 -- SEC. 498F. Prohibition Against Funding For Human Cloning». 10 de marzo de 2010. 
  47. ↑ «Human Cloning Laws». National Conference of State Legislatures (NCSL). Jan 2008. 
  48. ↑ Sleeper on IMDB
  49. ↑ Hopkins, Patrick. How Popular media represent cloning as an ethical problem. The Hastings Center. JSTOR 3527566. 
  50. ↑ «Yvonne A. De La Cruz ''Science Fiction Storytelling and Identity: Seeing the Human Through Android Eyes''» (PDF). Consultado el 19 de agosto de 2012. 

Further reading[editar]

  • Araujo, Robert John, “The UN Declaration on Human Cloning: a survey and assessment of the debate,” 7 The National Catholic Bioethics Quarterly 129 - 149 (2007).
  • Oregon Health & Science University. "Human skin cells converted into embryonic stem cells: First time human stem cells have been produced via nuclear transfer." ScienceDaily. ScienceDaily, 15 May 2013. <www.sciencedaily.com/releases/2013/05/130515125030.htm>.

External links[editar]


[[Category:Biotechnology] [[Category:Cloning]

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