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Expended definition


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Expended definition

  1. 1. Mariam Ekizyan: Sample of Technical WritingAn Expended Definition of Cloning for Non Technical ReadersAUDIENCE/ PURPOSE PROFILE This material is intended for an audience who has little or no priorknowledge of cloning. Though the terms “cloning” or “clone” are often used in today’s mass media, manyreaders may not know about the actual process of a cloning and its applications in agriculture andbiomedicine (application of the natural sciences to clinical medicine). This document will provide a generaloverview of cloning and will explain its history, procedure, types, uses, and limitations. As readers are notfamiliar with biomedicine, the definition will exclude the detailed explanation of human cloning, which is acomplex medical process, and ethical issues related to it.Expended Definition: CloningCloning is a biological process that is used to create a series of DNA, a cell, a tissue or an organism thathas genetically identical makeup as the original. The development of the new entity is done asexually: thatis, not involving the union of male and female germ (sperm or egg). The term “clone” originates from aGreek word klon meaning “a twig, spray” and is related to klados translated as “a young branch or anoffshoot of a plant” (Genetic Science Learning Center, 2010). According to the US National BioethicsAdvisory Commission (1997), cloning was always present in the natural world where many plants andsimple invertebrate (spineless) species, such as flowers or worms, regenerate asexually. However, the firstattempts to clone artificially occurred only in the 1880s. In 1894, Hans Driesch ran tests with a sea urchin’embryo that develops and grows outside their mother. During the experiment, Driesch shook the two celledembryo in a chemical glass container filled with sea water until it divided into two independent whole seaurchins. Since then, the technologies have developed a lot and many animals have been cloned, includingthe famous sheep Dolly in 1996, in Scotland.As the Genetic Science Learning Center (2010) illustrated, the process of cloning is similar to sexualreproduction as they both result in an embryo (fertilized egg) that consists of cells containing two completesets of chromosomes. These genetic codes, which have essential information for a living organism, are keptin a structure called a nucleus that acts like a human brain. The difference lies in the source of thesechromosomes. During sexual reproduction, both sperm and egg each contain one set of genetic codes.When they join, the embryo gets a unique set of DNA that includes a re-assortment of the genes from bothparents. In cloning, the two sets of the chromosomes come either from the father or from the mother. First,a somatic cell (any cell of the body) that contains a nucleus is taken out of the donor. Secondly, the nucleusis removed from the egg cell of the surrogate mother. Third, using an electric pulse, the empty egg is fusedwith the nucleus from a donor’s somatic cell that already contains both sets of X and Y chromosomes. Theembryo is then placed in a surrogate mother. Thus, the offspring inherits its donor’s identical DNA withoutany modifications. The procedure of cloning is shown in Figure 1. Figure 1. The Process of Cloning Source: Youngbloodbiology (2010). Cloning. Retrieved from https://youngbloodbiology.wikispaces .com/Cloning
  2. 2. 2This procedure serves as a framework for the three main types of cloning: reproductive, therapeutic andgenetic. 1. Reproductive cloning is used to create an animal that has the same DNA as the donor animal. The two methods of reproductive cloning include embryo separation and nuclear transplantation. During the method of the embryo separation, the fetus that has two to eight cells is divided soon after it is fertilized. The resulting embryos are then able to reproduce new organisms. This method is common in cattle breeding. Nuclear transplantation is similar to the overall cloning process, but the embryo is treated with electronic current or chemicals that cause its division (USNBAC, 1997). 2. Therapeutic cloning is the creation of human embryos that are later used in research. The objective is not to make a human clone, but rather gather stem cells. Stem cells can produce any type of specialized cells in the body. During this method, the empty egg is injected with skin cells instead of chromosomes. After this, a chemical is used to stimulate the egg development. After the fifth day of the embryo division, scientists remove these cells and use them to treat human diseases. (U.S. DEGP, 2009). 3. Genetic cloning refers to a process of creating multiple molecules by expending a DNA structure. It helps to produce multiple copies of a single gene in a very short period. To create a new DNA, scientists complete the following steps: they (a) break original DNA chains into fragments, (b) glue those pieces together in a desired sequence, (c) insert newly formed DNA into fast developing host organisms, such as bacteria (see Figure 2) (d) inject those organism into cells (e) select and collect the successfully injected cells with new DNA (USNBAC, 1997). Figure 2. DNA Genetic Cloning Source: Universe Review (2010). Mulitcellular Organisms. Retrieved from http://universe- three types of cloning are widely practiced in agriculture, medicine and research. Cloningtechnologies help scientists to learn more about the genetic structure of an organism and ways to modify it.For example, scientists try to develop farm plants with specific characteristics, such as better resistance toinsects, improved nutrition qualities, longer life spans and an ability to grow under water. In addition, genecloning offers an inexpensive way of producing vaccines and hormones that include hormone insulin fordiabetes or growth hormones. Reproductive cloning, in turn, can be an efficient way to repopulateendangered species or create animals with special qualities, such as drug-producing or genetically uniquemammals (USNBAC, 1997).
  3. 3. 3As Smith (2002) wrote, therapeutic cloning technology gives many benefits to medicine. Its primary usecan be to produce tissue or healthy cells in laboratories that can replace or repair cells or tissues which aremalfunctioning or are injured from Alzheimers or Parkinsons disease, diabetes or heart failure. Growingorgans from cloned human embryos would reduce the need for organ donation. Also, cloning can help totreat cancer, to rejuvenate and replace dead skin during cosmetic and plastic surgeries.Despite wide applications in research and biomedicine, cloning has some limitations, as stated by Dowty(2005). First, the number of organisms that can be reproduced from one embryo is limited as embryoniccells lose their qualities over time. Secondly, cloned organisms, especially animals, can face early agingsyndrome and have progressive diseases because nuclear transplantation is still developing and has itsweaknesses. That is why various cloned animals either died a week after birth or developed some type ofdisease. Thirdly, as a cloned organism gets its genes from its donor, then the clone will inherit all geneticdefects from its donor. For example, if a donor was infertile, then the clone will be infertile too. Lastly,although the clone is known as being the duplicate of a donor, it may not act or look the same as the donor,since not only genetic factors, but also the environment influences the clone. The social environment, likeculture, people and various institutions, in which a clone develops can affect its identity and modify itsbehavior. BibliographyDowty, R. (2005). Clones and Cloning. Science, technology, and society encyclopedia. (pp.54-55). New York: Oxford University Press.Genetic Science Learning Center at the University of Utah (2010). What is Cloning?. Retrieved from, S. (2002). The Benefits of Human Cloning. Retrieved October 18, 2010, from Department of Energy Genome Programs. (2009). Cloning Fact Sheet. Retrieved from States National Bioethics Advisory Commission. (1997). Cloning human beings: report and recommendations of the National Bioethics Advisory Commission (Vol.1). Rockville, MD: National Bioethics Advisory Commission