Cloning (Encyclopedia of Environmental Issues, Revised Edition)
The molecular cloning and engineering of deoxyribonucleic acid (DNA) molecules were first made possible with the discoveries of DNA ligase (enzymes that join DNA molecules) in 1967 and restriction endonucleases (enzymes that cut DNA molecules at specific nucleotide sequences) in 1970 by Hamilton Smith and Daniel Nathans. These enzymes allow scientists to cut and join DNA molecules from different species to produce recombinant DNA. For example, the DNA encoding human insulin can be combined with a plasmid, a small piece of DNA often found in bacteria such as Escherichia coli (E. coli). After the recombinant human-insulin-DNA/plasmid-DNA molecule is constructed, it can be inserted into a host cell such as E. coli. The recombinant DNA molecule will then replicate one or more times each time the E. coli DNA replicates. Thus a clone of identical recombinant human-insulin-DNA/plasmid-DNA molecules will result. If the recombinant molecule has been engineered with the requisite signals, the E. coli will produce copious amounts of human insulin. In 1972 the first recombinant DNA molecules were made at Stanford University, and in 1973 such molecules were inserted via plasmids into E. coli. The first successful synthesis of a human protein by E. coli was somatostatin, reported in 1977 by Keiichi Itakura and coworkers. In 1984 insulin was the first human protein made by E. coli to become...
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Environmental Impact of DNA Cloning (Encyclopedia of Environmental Issues, Revised Edition)
The construction of recombinant DNA molecules and their subsequent cloning have not been without controversy. In 1971 researcher Paul Berg planned an experiment to combine DNA from simian virus 40 (SV40)—a virus that causes tumors in monkeys and transforms human cells in culture—with bacteriophage l and to incorporate the recombinant molecule into E. coli. However, several scientists warned of a potential biohazard. Because E. coli is a natural inhabitant of the human digestive system, it was feared that the engineered E. coli could escape from the laboratory, enter the environment, become ingested by humans, and cause cancer as a result of its newly acquired DNA. The scientific community imposed a moratorium on recombinant DNA work in 1974 until the National Institutes of Health (NIH) could study the safety of recombinant DNA research and develop guidelines under which such work could proceed. The guidelines, originally published in 1976, were eventually relaxed after it was clearly demonstrated that the work was not nearly as dangerous as initially feared.
In 1983 the NIH granted permission to the University of California at Berkeley to release bacteria that had been engineered to protect plants from frost damage. This was the first experiment intentionally designed to introduce genetically engineered organisms into the environment. Various environmental and...
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Animal and Plant Cloning (Encyclopedia of Environmental Issues, Revised Edition)
The cloning of plants from cuttings has been successfully practiced for thousands of years and is commonly used for many important food crops. Successful animal cloning was first reported in 1892 by Hans Adolph Eduard Dreisch. Dreisch separated the first two and four embryonic cells (blastomeres) of the sea urchin and allowed them to develop into complete, genetically identical embryos.
The first report of successful animal cloning by nuclear transplantation was published in 1952 by Robert Briggs and Thomas J. King, who removed nuclei from embryonic frog cells and transplanted them into eggs from which their nuclei had been removed. By pricking the eggs with a glass needle the scientists induced them to divide and often develop into complete tadpoles. The first reliable reports of successful animal cloning by nuclear transplantation in mammals came in 1986 from Steen Willadsen in Cambridge, England. Willadsen cloned sheep from the nucleus of an early blastula cell. In 1987 Randall Prather and Willard Eyestone cloned cows while working in Neal First’s laboratory at the University of Wisconsin.
In 1997 Ian Wilmut and Keith Campbell announced that they had successfully cloned a sheep named Dolly in Edinburgh, Scotland, the year before. Dolly was a milestone in cloning research because she was the first mammal cloned from an adult cell. Such animal cloning makes genetic engineering more efficient, because an...
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Further Reading (Encyclopedia of Environmental Issues, Revised Edition)
Drlica, Karl. Understanding DNA and Gene Cloning: A Guide for the Curious. 4th ed. Hoboken, N.J.: John Wiley & Sons, 2004.
Fritz, Sandy, ed. Understanding Cloning. New York: Warner Books, 2002.
Klotzko, Arlene Judith. A Clone of Your Own? The Science and Ethics of Cloning. New York: Cambridge University Press, 2006.
Kolata, Gina Bari. Clone: The Road to Dolly, and the Path Ahead. New York: HarperCollins, 1998.
Williams, J. G., A. Ceccarelli, and A. Wallace. Genetic Engineering. 2d ed. Oxford, England: Bios, 2001.
Wilmut, Ian, Keith Campbell, and Colin Tudge. The Second Creation: Dolly and the Age of Biological Control. Cambridge, Mass.: Harvard University Press, 2001.
Wilmut, Ian, and Roger Highfield. After Dolly: The Uses and Misuses of Human Cloning. New York: W. W. Norton, 2006.
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Types of Cloning (Genetics & Inherited Conditions)
There are three different definitions of a clone. One is a group of genetically identical cells descended from a single common ancestor. This type of clone is often made by plant cell tissue culture in which a whole line of cells is made from a single cell ancestor. A second type of clone is a gene clone, or recombinant DNA clone, in which copies of a DNA sequence are made by genetic engineering. A third type of clone is an organism that is descended asexually from a single ancestor. A much-celebrated example of an organismal clone is the sheep Dolly (1997-2003), produced by placing the nucleus of a cell from a ewe’s udder, with its genetic material (DNA), into an unfertilized egg from which the nucleus had been removed.
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DNA CloningDNAcloning (Genetics & Inherited Conditions)
DNA is cloned to obtain specific pieces of DNA that are free from other DNA fragments. Clones of specific pieces of DNA are important for basic research. DNA is made up of four different compounds known as nucleotide bases. Once a piece of DNA is cloned, the specific DNA bases can be identified. This is called sequencing. Once this specific pattern of DNA sequencing is accomplished, the DNA is said to be “sequenced,” revealing the genetic code detailed by the nucleotide bases. This valuable information helps answer the following questions and can be used in a variety of ways. Where does the gene begin and end? What type of control regions does the gene have? Cloned DNAs can be used as hybridization probes, where sequences that are complementary to the cloned DNA can be detected. Such DNA hybridization is useful to detect similarities between genes from different organisms, to detect the presence of specific disease genes, and to determine in what tissues that gene is expressed. The gene is expressed when a messenger RNA (mRNA) is made from the gene and the mRNA is translated into a protein product. A DNA clone is also used to produce the protein product for which that gene codes. When a clone is expressed, the protein made by that gene can be studied or an antibody against that protein can be made. An antibody is used to show in which tissues of an organism that protein is found. Also, a DNA clone may be expressed because...
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Products of Recombinant DNA Technology (Genetics & Inherited Conditions)
Recombinant DNA technology has produced clones put to use for a wide variety of human purposes. For example, rennin and chymosin are used in cheese making. One of the most important applications, however, is in medicine. Numerous recombinant DNA products are useful in treating human diseases, including the production of human insulin (Humalin) for diabetics. Other human pharmaceuticals produced by gene cloning include clotting factor VIII to treat hemophilia A, clotting factor IX to treat hemophilia B, human growth hormone, erythropoietin to treat certain anemias, interferon to treat certain cancers and hepatitis, tissue plasminogen activator to dissolve blood clots after a heart attack or stroke, prolastin to treat genetic emphysemas, thrombate III to correct a genetic antithrombin III deficiency, and parathyroid hormone. The advantages of the cloned products are their high purity, greater consistency from batch to batch, and the steady supply they offer.
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How to Clone DNA (Genetics & Inherited Conditions)
DNA is cloned by first isolating it from its organism. Vector DNA must also be isolated from bacteria. (A vector is a plasmid or virus into which DNA is inserted.) Both the DNA to be cloned and the vector DNA are cut with a restriction enzyme that makes sequence-specific cuts in the DNAs. The ends of DNA molecules cut with restriction enzymes are then joined together with an enzyme called ligase. In this way the DNA to be cloned is inserted into the vector. These recombinant DNA molecules (vector plus random pieces of the DNA to be cloned) are then introduced into a host, such as bacteria or yeast, where the vector can replicate. The recombinant molecules are analyzed to find the ones that contain the cloned DNA of interest.
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Regulation of DNA Cloning (Genetics & Inherited Conditions)
In the 1970’s the tools to permit cloning of specific pieces of DNA were developed. There was great concern among scientists about the potential hazards of some combinations of DNA from different sources. Concerns included creating new bacterial plasmids with new drug resistances and putting DNA from cancer-causing viruses into plasmids. In February, 1975, scientists met at a conference center in Asilomar, California, to discuss the need to regulate recombinant DNA research. The result of this conference was the formation of the Recombinant DNA Molecule Program Advisory Committee at the National Institutes of Health, and guidelines for recombinant DNA work were established.
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Genetically Modified Organisms (Genetics & Inherited Conditions)
Numerous cloned genes have been introduced into different organisms to produce genetically modified organisms (GMOs). Genes for resistance to herbicides and insects have been introduced into soybean, corn, cotton, and canola, and these genetically engineered plants are in cultivation in fields in the United States and other countries. Fish and fruit and nut trees that mature more rapidly have been created by genetic engineering. Edible vaccines have been made—for example, a vaccine for hepatitis B in bananas. A tomato called the Flavr Savr is genetically engineered to delay softening. Plants that aid in bioremediation by taking up heavy metals such as cadmium and lead are possible.
Concerns about genetically modified organisms include safety issues—for example, concerns that foreign genes introduced into food plants may contain allergens and that the antibiotic resistance markers used in creating the GMOs might be transferred to other organisms. There are concerns about the environmental impact of GMOs; for example, if these foreign genes are transferred to other plants by unintended crossing of a GMO with a weed plant, weeds may become difficult or impossible to eradicate and jeopardize crop growth. There is a concern about the use of genetically modified organisms as food. There is a concern about loss of biodiversity if only one, genetically modified, variety of a crop plant is cultivated. There are also...
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Organismal CloningOrganismal cloning (Genetics & Inherited Conditions)
A goal of organismal cloning is to develop ways of efficiently altering animals genetically in order to reproduce certain animals that are economically valuable. Animals have been altered by the introduction of specific genes, such as human proteins that will create drug-producing animals. Some genes have been inactivated in organisms to create animal models of human diseases. For example, “knockout mice” are used as models for diabetes research. Another goal is to conduct research that might lead to the development of human organs for transplant produced from single cells. Similarly, animals might be genetically engineered to make their organs better suited for transplantation to humans. Finally, the cloning of a human might be a solution to human infertility.
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Are Organismal Clones Normal? (Genetics & Inherited Conditions)
There is, however, a concern about the health of cloned animals. First of all, when inserting a new nucleus into an egg from which the nucleus has been removed, and then implanting such eggs into surrogate mothers, only very few of the eggs develop properly. There are suggestions of other abnormalities in cloned animals that might be due to the cloning process. The first vertebrate to be successfully cloned, the sheep Dolly, developed first arthritis and then a lung disease when six years old; although neither condition was unusual in sheep, both appeared years earlier than normal, and Dolly was euthanized. Was she genetically older than her chronological age?
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Stem CellsStem cells (Genetics & Inherited Conditions)
Stem cells are unspecialized cells that are able to divide continuously and, with the proper conditions, be induced to give rise to specialized cell types. In the developing embryo they give rise to the hundreds of types of specialized cells that make up the adult body. Embryonic stem cells can be isolated from three- to five-day-old embryos. Some tissues in the adult, such as bone marrow, brain, and muscle, contain adult stem cells that can give rise to cell types of the tissue in which they reside.
A goal of research on stem cells is to learn how stem cells become specialized cells. Human stem cells could be used to generate tissues or organs for transplantation and to generate specific cells to replace those damaged as a result of spinal cord injury, stroke, burns, heart disease, diabetes, osteoarthritis, rheumatoid arthritis, and other conditions.
A 2009 study demonstrated that human corneal stem cells can repair cloudy corneas in mice. The cornea is the outermost portion of the eye and provides protection along with 70 percent of the eye’s focusing power. Deep corneal scratches can cause scarring that impairs vision. Mice treated with human stem cells cleared their corneas. Further study and investigation of this type of stem cell therapy could develop a potential stem cell therapy for corneal scarring in humans.
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Regulation of Organismal Cloning (Genetics & Inherited Conditions)
Until the cloning of the sheep Dolly in 1997, it was thought that adult specialized cells could not be made to revert to nonspecialized cells that can give rise to any type of cell. However, Dolly was created from a specialized adult cell from a ewe’s udder. After the publicity about Dolly, U.S. president Bill Clinton asked the National Bioethics Advisory Commission to form recommendations about the ethical, religious, and legal implications of human cloning. In June, 1997, that commission concluded that attempts to clone humans are “morally unacceptable” for safety and ethical reasons. There was a moratorium on using federal funds for human cloning. In January, 1998, the U.S. Food and Drug Administration (FDA) declared that it had the authority to regulate human cloning and that any human cloning must have FDA approval.
While there is general agreement in the United States and in many other countries that reproductive human cloning should be banned because of ethical and safety concerns, there is ongoing debate about whether or not to allow therapeutic cloning to treat human disease or research cloning to study how stem cells develop. The Human Cloning Prohibition Act of 2001 to ban both reproductive and therapeutic cloning passed in the U.S. House of Representatives, but the Senate did not support the ban. The ban was again considered by the lawmakers in 2002. In the meantime, individual states such...
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Further Reading (Genetics & Inherited Conditions)
Boylan, Michael. “Genetic Engineering.” In Medical Ethics, edited by Boylan. Upper Saddle River, N.J.: Prentice Hall, 2000. Considers the ethical concerns of gene therapy and organismal cloning. Tables, list for further reading.
Cibelli, Jose B., Robert P. Lanza, Michael D. West, and Carol Ezzell. “The First Human Cloned Embryo.” Scientific American 286, no. 1 (2002): 44-48. Describes the production of cloned early-stage human embryos and embryos generated only from eggs, not embryos.
Espejo, Roman, ed. Biomedical Ethics: Opposing Viewpoints. San Diego: Greenhaven Press, 2003. Presents debates about many aspects of organismal cloning. Illustrations, bibliography, index.
Fredrickson, Donald S. The Recombinant DNA Controversy, a Memoir: Science, Politics, and the Public Interest, 1974-1981. Washington, D.C.: ASM Press, 2001. An overview of the initial concerns about potential hazards of recombinant DNA cloning.
Klotzko, Arlene Judith, ed. The Cloning Sourcebook. New York: Oxford University Press, 2001. A collection of twenty-seven essays on the science, context, ethics, and policy issues surrounding cloning.
Kreuzer, Helen, and Adrianne Massey. Recombinant DNA and Biotechnology: A Guide for Teachers. Washington, D.C.: ASM Press, 2001. Descriptions of recombinant DNA cloning methods and applications. Illustrations, index.
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Web Sites of Interest (Genetics & Inherited Conditions)
Genetic Information Nondiscrimination Act of 2007. http://www.ornl.gov/sci/techresources/Human_Genome/publicat/GINAMay2008.pdf. The actual GINA law—protection meant to encourage increased genetic testing without fear of job loss or insurance complications.
Human Genome Project Information. http://www.ornl.gov/sci/techresources/Human_Genome/graphics/slides/talks.shtml. Includes links to two PowerPoint presentations. “Genomics and Its Impact on Science and Society: The Human Genome Project and Beyond” covers basic science, the Human Genome Project, what is known so far, next steps in genomic research, medicine, and benefits. “Beyond the Human Genome Project” covers what scientists have learned from the human genome sequence, what the next steps are in scientific discovery in genomics, and the diverse future applications of genomics.
1 Federal Register, Presidential Document Executive Order 13505 of March 9, 2009: “Removing Barriers to Responsible Scientific Research Involving Human Stem Cells”. http://edocket.access.gpo.gov/2009/pdf/E9-5441.pdf. Presidential directive to review and issue new NIH guidelines regarding scientific research and human stem cells.
Stem Cell Information. http://stemcells.nih.gov/info/basics. Comprehensive source of information from the National Institutes of Health on the biological properties of...
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Uses and Complications (Magill’s Medical Guide, Sixth Edition)
Scientists use the word “cloning” to indicate an experimental process by which an exact genetic duplicate is made of a molecule, cell, or organism. It is frequently divided into two general categories. Molecular cloning involves copying genes, short segments of DNA, or cells (sometimes also called cellular cloning) for the purpose of producing multiple copies of a molecule or cell for further scientific study. The cloning of DNA is commonly called recombinant DNA technology or genetic engineering. Cloning at the organismal level, also called nuclear transplantation, has been used to create genetically identical organisms and has the potential to produce genetically identical tissues and organs from a donor.
The procedure for molecular cloning involves choosing a vector for the study of the target DNA. The choice of the vector depends on the size of the genetic information being studied and whether it is genomic DNA or complementary DNA (cDNA). Common vectors include plasmids (small circular pieces of bacterial DNA), viruses, and artificial chromosomes. For example, if the length of the DNA being studied is small, then the researcher may choose to insert it into a plasmid. By the process of transformation, the selected plasmid is moved into the bacteria (usually E. coli), and as the bacteria divide, cells are produced that are clones for the DNA in the plasmid vector. If the researcher is unsure what area...
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Indications and Procedures (Magill’s Medical Guide, Sixth Edition)
By definition, the purpose of cloning is to produce genetically identical cells or individuals for scientific studies. Yet even identical, or monozygotic, twins, whose cells are derived from the same fertilized egg, are not truly identical. For example, monozygotic twins do not have the same fingerprint pattern, even though they possess the same genes for ridges on the fingers. The reason for this difference is environmental. For twins, the genes establish a general pattern, but it is the touch of the fingers on the inner wall of the uterus that establishes the final pattern of fingerprints. Environment plays a significant role in the development of the embryo, and this fact has presented a challenge for scientists who wish to produce identical genetic clones.
Dolly, a cloned ewe, was not an exact copy of her donor, even though she possessed the same genetic information as the donor ewe. The reason is that Dolly was raised in the uterus of a surrogate mother and thus was exposed to the minor, but important, environmental variations specific to the surrogate mother. It is known that, by a process called genomic imprinting, the mother can override certain traits in the embryo and impose her own traits, regardless of the genes present in the embryo. The mother also provides all the nutrients needed for the developing embryo, and thus any metabolic problems with the surrogate mother may inhibit proper development in...
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Perspective and Prospects (Magill’s Medical Guide, Sixth Edition)
While for many people the history of cloning may appear to have begun in 1996, when Ian Wilmut of the Roslin Institute in Scotland introduced the world to Dolly the cloned ewe, the reality is that the cloning of organisms had been going on for some time. The making of cloned plants had been occurring for decades and now represents a common occurrence in agriculture. If one restricts the discussion to animals, then Dolly does not really even represent the first cloned mammal, but rather the first adult animal cloned from the cells of another adult animal.
The cloning of animals by nuclear transplantation has its roots in the late nineteenth century, when early embryologists were studying cell division in the eggs of invertebrate animals. The first experiments that transferred a nucleus from one cell to another in a vertebrate animal were conducted in the early 1950’s by Robert Briggs and Thomas King. Briggs and King worked with nuclear transplantation in amphibians. These researchers were not interested in the creation of a cloned frog but rather the question of nuclear programming, or whether the cells isolated from the blastocyst had the genetic ability to form a new adult frog. These experiments examined the use of embryonic cells to produce a functionally adult organism.
In later experiments, researchers, including Briggs and King, set out to determine at what age of embryonic development cells...
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For Further Information: (Magill’s Medical Guide, Sixth Edition)
Cibelli, Jose, Robert Lanza, Michael West, and Carol Ezzell. “The First Human Cloned Embryo.” Scientific American 286 (January, 2002): 44-51. Discusses the process by which clones are generated for therapeutic purposes, as well as a new strategy for producing cloned cells using only unfertilized eggs. Illustrations of cloning procedures are included.
McKinnell, Robert, and Marie Di Berardino. “The Biology of Cloning: History and Rationale.” Bioscience 49 (November, 1999): 875-885. Reviews the history of cloning from the nineteenth century onward, including the scientific experiments that led to the cloning of amphibians and the advances in mammalian cloning.
National Institutes of Health. Department of Health and Human Services. Regenerative Medicine 2006. Bethesda, Md.: NIH Press, 2006. A collection of articles describing advances in stem cell and cloning technologies since this resource was first published in 2001.
Nussbaum, Martha, and Cass Sunstein, eds. Clones and Clones: Facts and Fantasies About Human Cloning. New York: W. W. Norton, 1999. A series of contributed essays on all aspects of human cloning, including science, ethics, and legal issues.
Pasternak, Jack J. An Introduction to Human Molecular Genetics. 2d ed. Hoboken, N.J.: Wiley-Liss, 2005. An excellent primer on many technologies as applied to humans, including genetic...
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Clone and Cloning (Encyclopedia of Science)
A clone is a cell, group of cells, or organism produced by asexual reproduction that contains genetic information identical to that of the parent cell or organism. Asexual reproduction is the process by which a single parent cell divides to produce two new daughter cells. The daughter cells produced in this way have exactly the same genetic material as that contained in the parent cell.
Although some organisms reproduce asexually naturally, the term "cloning" today usually refers to artificial techniques for achieving this result. The first cloning experiments conducted by humans involved the growth of plants that developed from grafts and stem cuttings. Modern cloning practices that involve complex laboratory techniques is a relatively recent scientific advance that is at the forefront of modern biology. Among these techniques is the ability to isolate and make copies of (clone) individual genes that direct an organism's development. Cloning has many promising applications in medicine, industry, and basic research.
History of cloning
Humans have used simple methods of cloning such as grafting and stem cutting for more than 2,000 years. The modern era of laboratory cloning began in 1958 when the English-American plant physiologist Frederick C. Steward (1904993) cloned carrot plants from mature single cells placed in a nutrient culture...
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Cloning (Encyclopedia of Science and Religion)
Cloning burst upon the scene in February, 1997, with the announcement of the birth of Dolly, the cloned sheep. She was created when researchers took the DNA nucleus from a cell of an adult sheep and fused it with an egg from another sheep. Shortly after Dolly was born, mice, cattle, goats, pigs, and cats were also cloned.
For biologists, however, the word cloning refers not to producing new animals but rather to copying DNA, including short segments such as genes or parts of genes. This ability to copy DNA is a basic technique of genetic engineering used in almost every form of research and biotechnology. In Dolly, copying was taken to the ultimate scale, the copying of the entire nucleus or the entire genome of the sheep. The transfer of the nucleus is usually called somatic cell nuclear transfer (SCNT), and this is what most people have in mind when they speak of cloning.
Dolly's birth immediately raised the question of human cloning. In principle, a human baby could be made using SCNT. The technical obstacles are, however, greater than most people recognize. Experts in the field doubt that human reproductive cloning can be safely pursued, at least for several decades. In Dolly's case, it took 277 attempts to create one live and apparently healthy sheep, a risk level that is clearly unacceptable for human reproduction. More important, the state of Dolly's health is not fully known. One fear associated with cloning is that the clone, having nuclear DNA that may be many years old, will age prematurely, at least in some respects. Mammalian procreation is a profoundly complicated process, as yet little understood, with subtlety of communication between sperm, egg, and chromosomes, which allows DNA from adults to turn back its clock and become, all over again, the DNA of a newly fertilized egg, an embryo, a fetus, and so forth through a complex developmental process. Using cloning to produce a healthy human baby who will become a healthy adult is decidedly beyond the ability of science as of 2002. Expert panels of scientists all strongly condemn the use of SCNT to produce a human baby.
Cloning, however, may have other human applications beside reproduction, and many scientists endorse these. Usually such applications are referred to as therapeutic cloning, but it should be noted that much research must occur before any therapy can be achieved. Especially interesting is the possibility of combining nonreproductive cloning with embryonic stem cell technologies. Human embryonic stem cells, first isolated in 1998, appear promising as a source of cells that can be used to help the human body regenerate itself. Based on research performed in mice and rats, scientists are optimistic that stem cells may someday be implanted in human beings to regenerate cells or tissues, perhaps anywhere in the body, possibly to treat many conditions, ranging from diseases such as Parkinson's to tissue damage from heart attack.
Embryonic stem cells are derived from embryos, which are destroyed in the process. Some scientists are hopeful that they will be able to find stem cells in the patient's own body that they can isolate and culture, then return to the body as regenerative therapy. Others think that stem cells from embryos are the most promising for therapy. But if implanted in a patient, embryonic stem cells would probably be rejected by the patient's immune system. One way to avoid such rejection, some believe, is to use SCNT. An embryo would be created for the patient using the patient's own DNA. After a few days, the embryo would be destroyed. The stem cells taken from the embryo would be cultured and put into the patient's body, where they might take up the function of damaged cells and be integrated into the body without immune response.
Religious concerns about cloning
While many believe the potential benefits justify research in therapeutic cloning, some object on religious grounds. Many Roman Catholic and Orthodox Christians reject this whole line of research because it uses embryos as instruments of healing for another's benefit rather than respecting them as human lives in their own right. Others believe that if nonreproductive cloning is permitted, even to treat desperately ill patients, then it will become impossible to prevent reproductive cloning, and so they want to hold the line against all human uses of SCNT. A few Protestant and Jewish groups and scholars have given limited approval to nonreproductive cloning.
Outside the United States, most countries with research in this area reject reproductive cloning but permit cloning for research and therapy. In the United States, federal funding is not available as of 2002 for any research involving human embryos. Privately funded research, however, faces no legal limits, even for reproductive cloning. In 2001, one U.S. corporate laboratory, Advanced Cell Technology, published its work, largely unsuccessful, to create human cloned embryos in order to extract stem cells. Some religious leaders object to this situation in which privately funded research is left unregulated.
When it comes to reproductive cloning, religious voices are nearly all agreed in their opposition, although they may give different reasons. Aside from a few isolated individuals, no one has offered a religious argument in support of reproductive cloning. All religious voices agree with the majority of scientists in their objection to cloning based on the medical risk that it might pose for the cloned person, who, even if born healthy, may experience developmental problems, including neurological difficulties, later in life. Until it is known that these risks are not significantly higher for the clone than for someone otherwise conceived, most scientists and ethicists agree that researchers have no right to attempt cloning.
Some religious scholars and organizations oppose cloning as incompatible with social justice. As an exotic form of medicine that benefits the rich, cloning should be opposed in favor of more basic health care and universal access to it.
Others oppose reproductive cloning because it goes against the nature of sexual reproduction, which has profound benefits for a species. Human beings are sexual beings, it is argued, and the necessity of sex for procreation is grounded in hundreds of millions of years of evolution and should not be lightly cast aside by technological innovation. Transcending the biological advantage of sexual procreation, some argue, are the moral and spiritual advantages of the unity of male and female in love, from which a new life emerges from the openness of being, far more than from the designs of will.
Some believe that cloning would confuse and probably subvert relationships between parents and their cloned children. If one person in a couple were the source of the clone's DNA, at a genetic level that parent would be a twin of the clone, not a parent. Whether biological confusion would amount to psychological or moral disorder is of course debatable, but any test might result in tragic consequences. Furthermore, cloning creates a child with nuclear DNA that, in some way at least, is already known. This nuclear DNA begins a new life, not with the usual uncertainties of sexual recombination but through the controls of technology. Many have said that the power to create a clone gives parents far too much power to define their children's genetic identity. Unlike standard reproductive medicine, even if combined in the future with technologies of genetic modification, cloning allows parents to specify that their child will have exactly the nuclear DNA found in the clone's original. This is assuredly not to say that parents may thereby select or control their child's personality or abilities, because persons are more than genes. But some fear that by its nature cloning moves too far in the direction of control and away from the unpredictability of ordinary procreation, so far in fact that a normal parent-child relationship cannot emerge in its proper course. To move in that direction at all is to risk subverting the virtues of parenting, such as unqualified acceptance.
Finally, some have held that cloning will place an unacceptable burden on the cloned child to fulfill the expectations that motivated their cloning in the first place. The fact that the parents may have some prior knowledge of how the clone's nuclear DNA was lived by the clone's original will lead the clone to think that the parents want a child with just these traits. One can imagine that clones will believe they are accepted and loved because they fulfill expectations and not because of their own unique and surprising identity.
In time, reproductive cloning may be widely accepted, much as in vitro fertilization has become accepted. But within religious communities, opposition to cloning is so strong that it is hard to imagine that religious people will ever accept it as a morally appropriate means of human procreation. Nevertheless, despite the strength of the objections, many recognize that human reproductive cloning will occur in time, and when it does the religious concern will shift from preventing cloning to affirming the full human dignity of the clone.
See also ANIMAL RIGHTS; BIOTECHNOLOGY; DNA; GENETIC ENGINEERING; REPRODUCTIVE TECHNOLOGY; STEM CELL RESEARCH
Brannigan, Michael C., ed. Ethical Issues in Human Cloning: Cross-disciplinary Perspectives. New York: Seven Bridges Press, 2001.
Bruce, Donald, and Bruce, Ann, eds. Engineering Genesis: The Ethics of Genetic Engineering in Non-Human Species. London: Earthscan, 1998.
Cole-Turner, Ronald, ed. Human Cloning: Religious Responses. Louisville, Ky.: Westminster John Knox Press, 1997.
Cole-Turner, Ronald, ed. Beyond Cloning: Religion and the Remaking of Humanity. Harrisburg, Pa.: Trinity Press International, 2001.
Hanson, Mark J., ed. Claiming Power over Life: Religion and Biotechnology Policy. Washington, D.C.: Georgetown University Press, 2001.
Kass, Leon R., and Wilson, James Q. The Ethics of Human Cloning. Washington, D.C.: AEI Press, 1998.
McGee, Glenn, ed. The Human Cloning Debate. Berkeley, Calif.: Berkeley Hills Books, 2000.
Nussbaum, M. C., and Sunstein, C. R., eds. Clones and Clones: Facts and Fantasies About Human Cloning. New York: Norton, 1998.
Pence, Gregory E. Who's Afraid of Human Cloning? Lanham, Md.: Rowman and Littlefield, 1998.
Pence, Gregory E., ed. Flesh of My Flesh: The Ethics of Cloning Humans. Lanham, Md.: Rowman and Littlefield, 1998.
Ruse, Michael, and Sheppard, Aryne, eds. Cloning: Responsible Science or Technomadness? Amherst, N.Y.: Prometheus, 2001.
Clone, Cloning (Encyclopedia of Drugs, Alcohol, and Addictive Behavior)
A clone is a group of organisms that derive from a single ancestor and are genetically identical. A clone can be a group of mammals such as sheep, or a group of cells in culture.
Cloning cells is a powerful tool in biology and medicine, since growing large quantities of identical cells allows for a large harvest of the various identical and useful components of these cells. It is possible to construct genetic components in the laboratory, place them in cells, and then have the cells grow and multiply to produce large quantities of the components.
Cloning is an essential technique in modern molecular biology; it is used widely in studying genetic effects in the drug-abuse field. Cloning much larger organisms such as cows and sheep is expected to have a major impact in that production of the best of any species can theoretically be accomplished by cloning. This is an important goal in agriculture today.
MICHAEL J. KUHAR