Expended definition
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This document provides a definition and overview of cloning for non-technical readers. Cloning is a biological process that creates genetically identical DNA, cells, tissues or organisms through asexual reproduction. There are three main types of cloning: reproductive cloning creates animals with the same DNA as a donor, therapeutic cloning creates human embryos for stem cell research, and genetic cloning produces multiple copies of a single gene. Cloning technologies are used in agriculture, medicine, and research to study genetics and develop modified organisms, though cloning still has limitations.
Expended definition
- 1. Mariam Ekizyan: Sample of Technical Writing An Expended Definition of Cloning for Non Technical Readers AUDIENCE/ PURPOSE PROFILE This material is intended for an audience who has little or no prior knowledge of cloning. Though the terms “cloning” or “clone” are often used in today’s mass media, many readers may not know about the actual process of a cloning and its applications in agriculture and biomedicine (application of the natural sciences to clinical medicine). This document will provide a general overview of cloning and will explain its history, procedure, types, uses, and limitations. As readers are not familiar with biomedicine, the definition will exclude the detailed explanation of human cloning, which is a complex medical process, and ethical issues related to it. Expended Definition: Cloning Cloning is a biological process that is used to create a series of DNA, a cell, a tissue or an organism that has genetically identical makeup as the original. The development of the new entity is done asexually: that is, not involving the union of male and female germ (sperm or egg). The term “clone” originates from a Greek word klon meaning “a twig, spray” and is related to klados translated as “a young branch or an offshoot of a plant” (Genetic Science Learning Center, 2010). According to the US National Bioethics Advisory Commission (1997), cloning was always present in the natural world where many plants and simple invertebrate (spineless) species, such as flowers or worms, regenerate asexually. However, the first attempts 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 celled embryo in a chemical glass container filled with sea water until it divided into two independent whole sea urchins. Since then, the technologies have developed a lot and many animals have been cloned, including the famous sheep Dolly in 1996, in Scotland. As the Genetic Science Learning Center (2010) illustrated, the process of cloning is similar to sexual reproduction as they both result in an embryo (fertilized egg) that consists of cells containing two complete sets of chromosomes. These genetic codes, which have essential information for a living organism, are kept in a structure called a nucleus that acts like a human brain. The difference lies in the source of these chromosomes. 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 both parents. 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 nucleus is removed from the egg cell of the surrogate mother. Third, using an electric pulse, the empty egg is fused with the nucleus from a donor’s somatic cell that already contains both sets of X and Y chromosomes. The embryo is then placed in a surrogate mother. Thus, the offspring inherits its donor’s identical DNA without any 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 This procedure serves as a framework for the three main types of cloning: reproductive, therapeutic and genetic. 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- review.ca/F10-multicell.htm#bone These three types of cloning are widely practiced in agriculture, medicine and research. Cloning technologies 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 to insects, improved nutrition qualities, longer life spans and an ability to grow under water. In addition, gene cloning offers an inexpensive way of producing vaccines and hormones that include hormone insulin for diabetes or growth hormones. Reproductive cloning, in turn, can be an efficient way to repopulate endangered species or create animals with special qualities, such as drug-producing or genetically unique mammals (USNBAC, 1997).
- 3. 3 As Smith (2002) wrote, therapeutic cloning technology gives many benefits to medicine. Its primary use can be to produce tissue or healthy cells in laboratories that can replace or repair cells or tissues which are malfunctioning or are injured from Alzheimer's or Parkinson's disease, diabetes or heart failure. Growing organs from cloned human embryos would reduce the need for organ donation. Also, cloning can help to treat 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 embryonic cells lose their qualities over time. Secondly, cloned organisms, especially animals, can face early aging syndrome and have progressive diseases because nuclear transplantation is still developing and has its weaknesses. That is why various cloned animals either died a week after birth or developed some type of disease. Thirdly, as a cloned organism gets its genes from its donor, then the clone will inherit all genetic defects 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, like culture, people and various institutions, in which a clone develops can affect its identity and modify its behavior. Bibliography Dowty, 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 http://learn.genetics.utah.edu/content/tech/cloning/whatiscloning/ Smith, S. (2002). The Benefits of Human Cloning. Retrieved October 18, 2010, from http://www.humancloning.org/benefits.php U.S. Department of Energy Genome Programs. (2009). Cloning Fact Sheet. Retrieved from http://www.ornl.gov/sci/techresources/Human_Genome/elsi/cloning.shtml#intro United 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