Cloning is the process of producing 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.
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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.
Molecular cloning refers to the procedure of isolating a defined DNA sequence and obtaining multiple copies of it in vivo. Cloning is frequently employed to amplify DNA fragments containing genes, but it can be used to amplify any DNA sequence such as promoters, non-coding sequences, chemically synthesised oligonucleotides and randomly fragmented DNA. Cloning is used in a wide array of biological experiments and technological applications such as large scale protein production.
Somatic cell nuclear transfer (SCNT) is a laboratory technique for creating a clonial embryo, using an ovum with a donor nucleus. It can be used in embryonic stem cell research, or, potentially, in regenerative medicine where it is sometimes referred to as "therapeutic cloning." It can also be used as the first step in the process of reproductive cloning.
Asexual reproduction is reproduction which does not involve meiosis, ploidy reduction, or fertilization. Only one parent is involved in asexual reproduction. A more stringent definition is agamogenesis which refers to reproduction without the fusion of gametes. Asexual reproduction is the primary form of reproduction for single-celled organisms such as the archaea, bacteria, and protists. Many plants and fungi reproduce asexually as well. While all prokaryotes reproduce asexually (without the formation and fusion of gametes), mechanisms for lateral gene transfer such as conjugation, transformation and transduction are sometimes likened to sexual reproduction. A lack of sexual reproduction is relatively rare among multicellular organisms, for reasons that are not completely understood. Current hypotheses suggest that, while asexual reproduction may have short term benefits when rapid population growth is important or in stable environments, sexual reproduction offers a net advantage by allowing more rapid generation of genetic diversity, allowing adaptation to changing environments.
Dolly (5 July 1996 – 14 February 2003) was a female domestic sheep remarkable in being the first mammal to be cloned from an adult somatic cell, using the process of nuclear transfer. She was cloned by Ian Wilmut, Keith Campbell and colleagues at the Roslin Institute near Edinburgh in Scotland. She was born on 5 July 1996 and she lived until the age of six. She has been called "the world's most famous sheep" by sources including BBC News and Scientific American.
Human cloning is the creation of a genetically identical copy of a human (not usually referring to monozygotic multiple births), human cell, or human tissue. The ethics of cloning is an extremely controversial issue. 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 cells from an adult for use in medicine and is an active area of research, while reproductive cloning would involve making cloned humans. Such reproductive cloning has not been performed and is illegal in many countries. 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.
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. As the science of cloning continues to advance, governments have dealt with ethical questions through legislation.
A cloning vector is a small piece of DNA into which a foreign DNA fragment can be inserted. The insertion of the fragment into the cloning vector is carried out by treating the vehicle and the foreign DNA with the same restriction enzyme, then ligating the fragments together. There are many types of cloning vectors. Genetically engineered plasmids and bacteriophages (such as phage λ) are perhaps most commonly used for this purpose. Other types of cloning vectors include bacterial artificial chromosomes (BACs) and yeast artificial chromosomes (YACs).
Pet cloning is the commercial cloning of a pet animal. The first commercially cloned pet was a cat named Little Nicky, produced in 2004 by Genetic Savings & Clone for a north Texas woman for the fee of US$50,000. On May 21, 2008 BioArts International announced a limited commercial dog cloning service through a program it calls Best Friends Again. This program came on the announcement of the successful cloning of a family dog Missy, which was widely publicized in the Missyplicity Project. In September 2009 BioArts announced the end of its dog cloning service.
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