Transcript Document
By: Dean Aszman, Nishit Patel, Jonathan Pekar, and Robby Lancaster Table Of Contents •History of Cloning •Reproductive Cloning •Therapeutic Cloning •DNA Cloning •Timeline Of Cloning •Vocabulary •Opinion •Bibliography History of Cloning Cloning is not new. Experiments with frogs and toads date back to the 1970s . And experiments involving plants and animal embryos have been performed for years. But experiments involving human beings have never been tried or thought possible, until "Dolly." Her birth shocked the scientific community and has spurred discussion about the possibility of human clones. Dr. Lee Silver, a molecular biologist at Princeton University, is optimistic that "human cloning will occur," and that "it might take five years, ten years at the outermost." Lee notes that at this time, "no ethical doctor would do human cloning“.Although this view is predominant among many scientists, some argue that a safe technology could be developed in the future. This has led to discussion about whether human cloning should even be legally possible. Reproductive Cloning Reproductive cloning is a technology used to generate an animal that has the same nuclear DNA as another currently or previously existing animal. Dolly was created by reproductive cloning technology. In a process called "somatic cell nuclear transfer" (SCNT), scientists transfer genetic material from the nucleus of a donor adult cell to an egg whose nucleus, and thus its genetic material, has been removed. The reconstructed egg containing the DNA from a donor cell must be treated with chemicals or electric current in order to stimulate cell division. Once the cloned embryo reaches a suitable stage, it is transferred to the uterus of a female host where it continues to develop until birth. Therapeutic Cloning Therapeutic cloning, also called "embryo cloning," is the production of human embryos for use in research. The goal of this process is not to create cloned human beings, but rather to harvest stem cells that can be used to study human development and to treat disease. Stem cells are important to biomedical researchers because they can be used to generate virtually any type of specialized cell in the human body. Stem cells are extracted from the egg after it has divided for 5 days. The egg at this stage of development is called a blastocyst. The extraction process destroys the embryo, which raises a variety of ethical concerns. Many researchers hope that one day stem cells can be used to serve as replacement cells to treat heart disease, Alzheimer's, cancer, and other diseases. In November 2001, scientists from Advanced Cell Technologies (ACT), a biotechnology company in Massachusetts, announced that they had cloned the first human embryos for the purpose of advancing therapeutic research. To do this, they collected eggs from women's ovaries and then removed the genetic material from these eggs with a needle less than 2/10,000th of an inch wide. A skin cell was inserted inside the enucleated egg to serve as a new nucleus. The egg began to divide after it was stimulated with a chemical called ionomycin. The results were limited in success. Although this process was carried out with eight eggs, only three began dividing, and only one was able to divide into six cells before stopping. DNA Cloning •DNA cloning is the transfer of a DNA fragment from one organism to a self duplicating element such as a bacterial plasmid •Scientists studying a particular gene often use bacterial plasmids to create copies of a type of gene •Plasmids are self-duplicating extra chromosomal circular DNA molecules •To duplicate a gene, a DNA fragment of that gene is taken as a sample, or removed, from chromosomal DNA using restriction enzymes and then combined with a plasmid that has already been taken by the same restriction enzymes Pros and Cons of Cloning Human Cloning Pros •There is no better way to understand the human genome •Ability to produce “superhumans” •Medical methods will be boosted by generations •More elaborate understanding of our past •There will be no more of a wait for organ transplants Cons •Humans are not made to be guinea pigs and they are of free will • Ability to produce “superhumans” •Countries could clone armies •If humans can be cloned then they can be sold, which is inhumane •If everyone has the same genotype, then a fatal disease that only effects that genotype could wipe out the human race Timeline Of Cloning 1885 1888 August Weismann, professor of zoology and comparative anatomy at the University of Freiberg, theorized that the genetic information of a cell would diminish as the cell went through differentiation. Timeline cont. Wilhelm Roux tested the germ plasma theory for the first time. One cell of a 2-cell frog embryo was destroyed with a hot needle; the result was a half-embryo, supporting Weismann's theory. 1894 Hans Dreisch isolated blastomeres from 2- and 4-cell sea urchin embryos and observed their development into small larvae. These experiments were regarded as refutations of the Weismann-Roux theory. 1901 Hans Spemann split a 2-cell newt embryo into two parts, resulting in the development of two complete larvae. Timeline cont. 1902 German embryologist Hans Spemann split a 2-celled salamander embryo and each cell grew to adulthood, providing proof that early embryo cells carry necessary genetic information. This finally disproved Weismann's 1885 theory that the amount of genetic information in cells decreases with each division. 1914 Hans Spermann conducted and early nuclear transfer experiment. 1928 Hans Spemann performed further, successful nuclear transfer experiments. 1938 Hans Spemann published the results of his 1928 primitive nuclear transfer experiments involving salamander embryos in the book "Embryonic Development and Induction." Spemann argued the next step for research should be the cloning organisms by extracting the nucleus of a differentiated cell and putting it into an enucleated egg. 1944 Oswald Avery found that a cell's genetic information was carried in DNA. 1950 First successful freezing of bull semen at -79°C for later insemination of cows was accomplished. First animal cloning: Robert Briggs and Thomas J. King cloned northern leopard frogs. Francis Crick and James Watson ,working at Cambridge's Cavendish Laboratory, discovered the structure of DNA. 1952 1953 Timeline Cont. 1972 Paul Berg combined the DNA of two different organisms, thus creating the first recombinant DNA molecules. 1973 Stanley Cohen and Herbert Boyer created the first recombinant DNA organism using recombinant DNA techniques pioneered by Paul Berg. Also known as gene splicing, this technique that allows scientists to manipulate the DNA of an organism - the basis of genetic engineering. 1977 Karl Illmensee and Peter Hoppe created mice with only a single parent. 1978 David Rorvik published the novel In His Image: The Cloning of a Man. 1978 Baby Louise, the first child conceived through in vitro fertilization, was born. Timeline Cont. 1979 Karl Illmensee claimed to have cloned three mice. 1980 In the case Diamond v. Chakrabarty, the United States Supreme Court ruled that a "live, human made microorganism is patent able material." 1983 Kary B. Mullis developed the polymerize chain reaction (PCR) in 1983. This process allows for the rapid synthesis of designated fragments of DNA. 1983 Davor Solter and David McGrath tried to clone mice using their own version of the nuclear transfer method. 1983 The first human mother-to-mother embryo transfer was completed. 1983 - 86 Marie A. Di Berardino, Nancy H. Orr, and Robert McKinnell transplanted nuclei of adult frog erythrocytes, thus obtained pre-feeding and feeding tadpoles. 1984 Steen Willadsen cloned a sheep from embryo cells, the first verified example of mammal cloning using the process of nuclear transfer. Vocabulary Biodegradable- able to break down and be reabsorbed by the environment Cell- the basic building block of life Chromosome- the structure that contains genes DNA Clone- an organism that has the same genes as another organism Cloning- using genes to make a copy of an organism DNA- a chemical substance that give instructions to cells Electron microscope- a tool used to study extremely small objects such as cells and genes Gene- a section of DNA that passes traits from parent to offspring Gene Testing- tests to find damage or missing genes Gene Therapy- using genetic engineering to fight or cure a disease Genetic engineering- placing a section of DNA from one organism to another Genetics- The study of genes, DNA, and heredity Heredity- The passing of traits from parent to offspring Membrane- the outer part of a cell Nucleus- a pouch inside the cell that contains the DNA Trait- A characteristic Our Opinion We think that there should not be human cloning. It would be inhumane because they become slaves to us. Also, if everyone made clones eventually we would all have the same genotype. Wars could never end because both sides would keep cloning their armies. And once we all have one genotype, there may be disease that are fatal to this genotype. The only good thing about cloning is that we would always be able to make an organ if somebody needs an organ transplant. Bibliography • • • • http://atheism.about.com/library/chronologies/blchron_sci_cloning.htm Life in the Future: Cloning and Genetic Engineering; 2002; by Holly Crefey http://www.ornl.gov/sci/techresources/Human_Genome/elsi/cloning.shtml http://library.thinkquest.org/18258/cloning.htm