Restriction Enzymes (Genetics & Inherited Conditions)
Many of the methods used in genetic engineering represent adaptations of naturally occurring genetic processes. One of the earliest and most significant discoveries was the identification of a family of DNA enzymes called restriction endonucleases, more commonly called restriction enzymes. Restriction enzymes are DNA-modifying enzymes produced by microorganisms as a protection against viral infection; their uniqueness and utility in recombinant DNA technology reside in their ability to cleave DNA at precise recognition sites based on DNA sequence specificity. Several hundred restriction enzymes have been isolated, and many recognize unique DNA segments and initiate DNA cleavage only at these sites. The site-specific cleavages generated by restriction enzymes can be used to produce a unique set of DNA segments that can be used to “map” individual genes and distinguish them from all other genes. This type of genetic analysis, based on differences in the sizes of DNA segments from different genes or different individuals when cleaved with restriction enzymes, is referred to as restriction fragment length polymorphism (RFLP) analysis.
If genes or DNA segments from different sources or species are cleaved with the same restriction enzyme, the DNA segments produced, though genetically unrelated, can be mixed together to produce recombinant DNA. This occurs because most restriction enzymes produce complementary, linear,...
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Vectors (Genetics & Inherited Conditions)
Plasmids are small, circular DNAs that have been isolated from many species of bacteria. These naturally occurring molecules often encode antibiotic resistance genes that can be transferred from one bacterial cell to another in a process called transformation. In the laboratory, plasmids can be used as vectors in the amplification of genes inserted by restriction enzyme treatment of both vector and insert DNA, followed by DNA ligation to produce recombinant plasmids. The recombinant DNA is then inserted into host bacterial cells by transformation, a routine process in which bacterial cells are made “competent,” that is, able to take up DNA from their surroundings. Once inside the host cell, the recombinant plasmid will be replicated by the host cell, along with the host’s own genome. Bacterial cells reproduce rapidly and generate large colonies of cells, each cell containing a copy of the recombinant plasmid. By this process the fragment of DNA in the recombinant vector is “cloned.”
The cloned DNA can then be isolated from the bacterial cells and used for other applications or studies. Plasmids are useful for cloning small genes or DNA fragments; larger fragments can be cloned using viral vectors such as the bacterial virus (bacteriophage) lambda (phage λ). This virus can infect bacterial cells and reproduce a high number of copies of itself. If nonessential viral genes are removed, recombinant viruses containing genes of...
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DNA Sequence AnalysisDNA sequencing technology (Genetics & Inherited Conditions)
A further key discovery in genetic engineering has been the development of chemical methods of DNA sequence analysis. These methods permit a determination of the linear sequence of nucleotide bases in DNA. DNA sequence analysis permits a direct determination of gene structure with respect to regulatory and protein-coding regions and can be used to predict the structure and function of proteins encoded by specific genes.
There are many important applications of the basic principles of genetic engineering. Notable examples include the Human Genome Project, the identification and characterization of human disease genes, the production of large amounts of proteins for therapeutic or industrial purposes, the creation of genetically engineered plants that are disease-resistant and show higher productivity, the creation of genetically engineered microorganisms that can help clean up pollution, and the treatment of genetic disorders using gene therapy.
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Gene Cloning (Genetics & Inherited Conditions)
The ability to clone DNA fragments has directly facilitated DNA sequence analysis. In addition to allowing the better understanding of specific genes, cloning was an integral tool in the Human Genome Project, an international effort to elucidate the structure of the entire human genome. The Human Genome Project offers the promise of greatly increasing the understanding of the genes responsible for inherited single-gene disorders as well as the involvement of specific genes in multifactorial disorders such as coronary heart disease.
The underlying genetic defects for a number of disease-causing genes have been identified, including sickle-cell disease (which results from a single nucleotide base substitution in one of the globin genes), Duchenne muscular dystrophy (caused by deletions in the muscle protein gene for dystrophin), and cystic fibrosis (caused by a variety of mutations in the gene for the chloride channel conductance protein). The identification of these disease genes has permitted the design of diagnostic tests and in some cases therapeutic strategies, including attempts to replace defective genes.
The analysis of gene function has been made possible by a process called site-directed mutagenesis, in which specific mutations can be introduced into cloned genes. These mutant genes can then be inserted into expression vectors, where the faulty protein can be produced and studied. Alternatively, the mutant genes...
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Transgenic OrganismsTransgenic organisms (Genetics & Inherited Conditions)
One of the earliest successes in producing transgenic organisms was when Escherichia coli bacteria were engineered to produce human insulin for the treatment of diabetes. The technology involved the cloning of the human insulin gene and its insertion into bacterial expression vectors. Subsequently, many gene products have been produced by genetically engineered microorganisms, including clotting factors (used in the treatment of hemophilia), growth factors such as epidermal growth factor (used to accelerate wound healing) and colony-stimulating factors (used to stimulate blood cell formation in the bone marrow), and interferons (used in the treatment of immune-system disorders and certain types of cancer). The advantages of using genetically engineered products are enormous: Therapeutic proteins or hormones can be produced in much larger amounts than could be obtained from tissue isolation, and the genetically engineered products are free of viruses and other contaminants.
Introduction of foreign genes into the fertilized eggs of host animals is called germ-line transformation and involves the insertion of individual genes into fertilized eggs. After the eggs are implanted in foster mothers, the resulting transgenic offspring will have the mutated gene in all their cells and will be able to pass the gene on to their future offspring.
Many of the methods for introducing foreign genes...
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Genetically Engineered Viruses (Genetics & Inherited Conditions)
An additional medical application involves the use of genetically engineered viruses in the treatment of genetic diseases. Retroviruses are the most important group of viruses used for these purposes, since the life cycle of the virus involves the incorporation of the viral genome into host chromosomes. Removal of most of the virus’s own structural genes removes its ability to cause disease, while the regulatory genes are retained and ligated to the therapeutic gene. The recombinant retrovirus then becomes harmless; however, it can still enter a cell and become integrated into the host cell genome, where it can direct the expression of the therapeutic gene. The first successful clinical application was the use of genetically engineered retroviruses in the treatment of severe combined immunodeficiency disorder (SCID). Viruses with a functional copy of the ADA gene were able to reverse SCID. However, in 2002 researchers in France and the United States discovered that this treatment appears to lead to a greatly increased risk of developing leukemia, and clinical trials were suspended.
Similar methods have been used to develop recombinant vaccines. For example, a recombinant vaccinia virus has been produced by the insertion of genes from other viruses. During the process of infection, the recombinant vaccinia virus produces proteins from the foreign genes, which act as antigens which lead to immunity...
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Impact and Applications (Genetics & Inherited Conditions)
The methods of recombinant DNA technology have revolutionized the understanding of the molecular basis of life and have led to a variety of useful applications. Some of the most important discoveries have involved an increased understanding of the molecular basis of disease processes, which has led to new methods of diagnosis and treatment. Genetically engineered animals can be used to produce unlimited amounts of therapeutic gene products and can also serve as genetic models to enhance understanding of the physiological basis of disease. Plants can be genetically engineered for increased productivity and disease resistance. Genetically engineered viruses have been developed as vaccines against infectious disease. The methods of recombinant DNA technology were originally developed from natural products and processes that occur within the living system. The ultimate goals of this research must involve applications that preserve the integrity and continuity of the living system.
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Further Reading (Genetics & Inherited Conditions)
Altieri, Miguel A. Genetic Engineering in Agriculture: The Myths, Environmental Risks, and Alternatives. 2d ed. Oakland, Calif.: Food First Books/Institute for Food and Development Policy, 2004. Raises serious questions about the drive toward genetically engineered crops.
Boylan Michael, and Kevin E. Brown. Genetic Engineering: Science and Ethics on the New Frontier. Upper Saddle River, N.J.: Prentice Hall, 2001. Written by a biologist and a philosopher, this text includes discussion of the professional and practical principles of conduct, the biology of genetic therapy, the limits of science, somatic gene therapy, enhancement, cloning, and germ-line therapy. Illustrated.
Drlica, Karl. Understanding DNA and Gene Cloning: A Guide for the Curious. 4th ed. Hoboken, N.J.: Wiley, 2004. An excellent introduction to the basic properties of DNA and its current applications. Consists of five sections: basic molecular genetics, manipulating DNA, molecular genetics, human genetics, and whole genomes.
Heller, Knut J., ed. Genetically Engineered Food: Methods and Detection. 2d updated and enlarged ed. Weinheim, Germany: Wiley-VCH, 2006. Covers methods and applications for creating genetically engineered food, including transgenic modification of production traits in farm animals, fermented food production, and the production of food additives using filamentous fungi. Examines legal issues...
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Web Sites of Interest (Genetics & Inherited Conditions)
Centers for Disease Control, Office of Genomics and Disease Prevention. http://www.cdc.gov/genomics/default.htm. Offers information on the genetic discoveries and prevention of diseases in humans. Includes links to related resources.
Human Genome Project. http://www.ornl.gov/sci/techresources/Human_Genome/elsi/gmfood.shtml. Fact sheet providing an introduction to genetically modified foods and organisms, listing the benefits and controversies of genetic engineering and offering links to other resources.
Scientific American. http://www.scientificamerican.com/topic.cfm?id=genetic-engineering. This page in the online edition of the magazine provides news items, podcasts, slide shows, blogs, and other information about genetic engineering.
U.S. Department of Agriculture, Biotechnology. http://desearch.nal.usda.gov/cgi-bin/dexpldcgi?qry1267112447;2. Provides information about the department’s biotechnology research programs and links to other sites about agricultural biotechnology.
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Genetic Engineering and Human Health (Magill’s Medical Guide, Sixth Edition)
Genetic engineering, recombinant DNA technology, and biotechnology constitute a set of techniques used to achieve one or more of three goals: to reveal the complex processes of how genes are inherited and expressed, to provide better understanding and effective treatment for various diseases (particularly genetic disorders), and to generate economic benefits, which include improved plants and animals for agriculture and the efficient production of valuable biopharmaceuticals. The characteristics of genetic engineering possess both vast promise and potential threats to humankind. It is an understatement to say that genetic engineering will revolutionize medicine and agriculture in the twenty-first century. As this technology unleashes its power to have an impact on daily life, it will also bring challenges to ethical systems and religious beliefs.
Soon after the publication of the short essay by Francis Crick and James Watson on DNA structure in 1953, research began to uncover the way by which DNA molecules can be cut and spliced back together. With the discovery of the first restriction endonuclease by Hamilton Smith and colleagues in 1970, the real story of genetic engineering began to unfold. The creation of the first engineered DNA molecule through the splicing together of DNA fragments from two unrelated species was made public in 1972. What soon followed was an array of recombinant DNA molecules and...
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Genetic Engineering in Agriculture, Forensics, and Environmental Science (Magill’s Medical Guide, Sixth Edition)
As the use of genetic engineering expands rapidly, it is difficult to generate an exhaustive list of all possible applications, but three other areas are worth noting: forensic, environmental, and agricultural applications. Although these areas are not directly related to medicine, they certainly have profound impacts on human well-being. There are numerous ways that genetic engineering may be used to benefit agriculture and food production. First, the production of vaccines and the application of methods for transferring genes is likely to benefit animal husbandry, as scientists can alter commercially important traits such as milk yield, butterfat, and proportion of lean meat. For example, the bovine growth hormone produced through genetic engineering has been used since the late 1980’s to boost milk production by cows. A mutant form of the myostatin gene has been identified and found to cause heavy muscling after this gene was introduced first into a mouse and later into the Belgian Blue bull. This technique marks the first step toward breeding cows and meat animals with lower fat and a higher proportion of lean meat. Other examples of using genetic engineering in animal husbandry include hormones for a faster growth rate in poultry and the production of recombinant human proteins in the milk of livestock.
Second, genetic engineering is expected to alter...
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Perspective and Prospects (Magill’s Medical Guide, Sixth Edition)
Since the discovery of the double-helical structure of DNA by Francis Crick and James Watson in 1953, human curiosity regarding this amazing molecule has propelled the advancement of biological sciences in an unprecedented fashion. The first successful experiment in genetic engineering was described in 1972 when DNA fragments from two different organisms were joined together to produce a biologically functional hybrid DNA molecule. The next milestone came in 1975, when Edward Southern introduced Southern blotting, a technique that has many applications and has proved invaluable for the subsequent development of genetic engineering. This technique is used to identify a particular gene or DNA fragment from a mixture of thousands of different genes or DNA fragments. Later, the automated DNA sequencers, which can rapidly churn out letter sequences from DNA fragments, and the discovery of reverse transcriptase and PCR further improved the capabilities of scientists in studying and manipulating DNA molecules and the genes that they carry.
Using these techniques, the first prenatal diagnosis of a genetic disease was made in 1976 for alpha-thalassemia, a genetic disorder caused by the absence of globin genes. This represented a monumental step forward in the use of genetic tools in the medical field. It paved the way for the later development in which mutations in many genes could be detected in early pregnancy. Three years...
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For Further Information: (Magill’s Medical Guide, Sixth Edition)
Brungs, Robert S. J., and R. S. M. Postiglione, eds. The Genome: Plant, Animal, Human. St. Louis, Mo.: ITEST Faith/Science Press, 2000. A collection of excellent scientific, ethical, educational, and theological papers focuses on the genomic revolution and the application of genetic engineering to plants, humans, and other animals.
Daniell, H., S. J. Streatfield, and K. Wycoff. “Medical Molecular Farming: Production of Antibodies, Biopharmaceuticals, and Edible Vaccines in Plants.” Trends in Plant Science 6 (2001): 219-226. A contemporary review of the production of plant-based medicinal products through genetic engineering and related biotechnology.
Frankel, M. S., and A. Teich, eds. The Genetic Frontier. Washington, D.C.: American Association for the Advancement of Science, 1994. A wonderful collection of essays from many experts and organizations dealing with the ethics, laws, and policies of genetic engineering.
Gerdes, Louise I., ed. Genetic Engineering: Opposing Viewpoints. Farmington Hills, Mich.: Greenhaven Press, 2004. Presents balanced and well-thought-out opposing views on genetic engineering by proponents and opponents from various angles.
Holland, Suzanne, Karen Lebacqz, and Laurie Zoloth, eds. The Human Embryonic Stem Cell Debate: Science, Ethics, and Public Policy. Cambridge, Mass.: MIT Press, 2001. Very thoughtful reflections on...
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Genetic Engineering (Encyclopedia of Science)
Genetic engineering is any process by which genetic material (the building blocks of heredity) is changed in such a way as to make possible the production of new substances or new functions. As an example, biologists have now learned how to transplant the gene that produces light in a firefly into tobacco plants. The function of that genehe production of lightas been added to the normal list of functions of the tobacco plants.
The chemical structure of genes
Genetic engineering became possible only when scientists had discovered exactly what is a gene. Prior to the 1950s, the term gene was used to stand for a unit by which some genetic characteristic was transmitted from one generation to the next. Biologists talked about a "gene" for hair color, although they really had no idea as to what that gene was or what it looked like.
That situation changed dramatically in 1953. The English chemist Francis Crick (1916) and the American biologist James Watson (1928) determined a chemical explanation for a gene. Crick and Watson discovered the chemical structure for large, complex molecules that occur in the nuclei of all living cells, known as deoxyribonucleic acid (DNA).
DNA molecules, Crick and Watson announced, are very long chains or units made of a combination of a simple sugar and a phosphate group.
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Genetic Engineering (West's Encyclopedia of American Law)
The human manipulation of the genetic material of a cell.
Genetic engineering involves isolating individual DNA fragments, coupling them with other genetic material, and causing the genes to replicate themselves. Introducing this created complex to a host cell causes it to multiply and produce clones that can later be harvested and used for a variety of purposes. Current applications of the technology include medical investigations of gene structure for the control of genetic disease, particularly through antenatal diagnosis. The synthesis of hormones and other proteins (e.g., growth hormone and insulin), which are otherwise obtainable only in their natural state, is also of interest to scientists. Applications for genetic engineering include disease control, hormone and protein synthesis, and animal research.
International Codes and Ethical Issues for Society
An international code of ethics for genetic research was first established in the World Medical Association's Declaration of Helsinki in 1964. The guide prohibited outright most forms of genetic engineering and was accepted by numerous U.S. professional medical societies, including the AMERICAN MEDICAL ASSOCIATION (AMA).
In 1969 the AMA promulgated its own ethical guidelines for clinical investigation, key provisions of which conflicted with the Helsinki...
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Genetic Engineering (Encyclopedia of Nursing & Allied Health)
Genetic engineering involves altering the genetic structure of embryonic cells or vectors to provide them with desired traits or to eliminate undesirable traits.
For thousands of years, humans have engaged in primitive forms of genetic engineering. They have chosen plants or animals with survival strength and desirable characteristics for further breeding, and have combined different strains of a species in attempts to retain and emphasize desirable characteristics of both. But in the 1970s, the field of genetic engineering took a quantum technologic leap when researchers developed a technique known as recombinant DNA, or gene splicing, enabling them to directly alter the genetic code and sequence of cells. This development transformed genetic engineering in medicine, food production, and industry. Engineered bacteria are even being used to take the place of standard microchip circuitry for computers.
Genes, which are composed of molecules of DNA, determine the physical characteristics that make organisms unique. Gene splicing, which involves introducing new genes into an organism in order to produce new characteristics, is performed in a number of ways. Sometimes a DNA "gun" is used to shoot genes directly into cells such as plant cells. When a gene cannot be directly "cut and pasted" from one organism to another, it may be placed in a harmless bacterium that duplicates repeatedly, acting as a "gene factory." The bacteria are then used to ferry the genes into cells.
A sheep named Dolly, born in 1997, was produced using a genetic engineering technique known as cloning. Here, scientists replaced the genetic material from one ewe's egg with genetic material from another ewe, producing an animal genetically unrelated to its surrogate mother. Hundreds of animals have been cloned, including bulls, cows, mice, monkeys, and pigs. Even clones of clones have been produced. Cloning is used to produce laboratory test animals with specific disease-related characteristics. Areas of cloning research range from cloning cows and sheep to produce medicines in their milk, to using cloning to preserve endangered species such as the Indian cheetah and the Asian guar.
Genetic engineering techniques are used to produce several widely used drugs. In addition to the hormone insulin, used to treat some forms of diabetes, these techniques are now used to produce the following: interferon, an antiviral and anticancer drug; tissue plasminogen activator (tPA), which dissolves blood clots; erythropoetin, which stimulates red blood-cell production; a hepatitis B vaccine; and others. In food production, genetic engineering can produce tomatoes with a longer shelf life; as well as crops with insect, herbicide, frost, and virus resistance. It is used to increase milk production in dairy cows, and to increase the size and infection-resistance of farmed fish like salmon. In addition, genetically altered bacteria have been used to decompose garbage and petroleum products.
Despite all its advances, the field of genetic engineering is still in its infancy. Now that researchers have mapped much of the human genome (or DNA blueprint), and some of the genes and their mutations responsible for genetic disorders like cystic fibrosis have been found, the next challenge is to understand proteins. These are the most complex of all known molecules. Each of the body's genes carries the code to create many different proteins (peptides), which are essentially the workers that carry out the DNA instructions. Understanding how messenger
proteins work is essential to preventing or curing disease. This will be a major focus of research over the next decade.
Promising areas of genetic engineering include human gene therapy and stem-cell research. Gene therapy involves repairing or replacing mutated genes in order to correct the malfunctions in protein production that can lead to disease. The use of gene therapy is being researched for diseases such as cancer, muscular dystrophy, hemophilia B, heart disease, and severe combined immune deficiency disease (known as "bubble boy disease"), among others. Stem cells are the undifferentiated cells from which specialized embryonic cells develop. They are considered one of science's best hopes for curing disease. Modified stem cells may one day be used to replace diseased cells affecting function throughout the body's systems. These cells also play an important role in tissue engineering, which involves the manufacture of blood products; artificial skin products; and biogenetic
replacement of organs, blood vessels, and cartilage. Other examples of genetic engineering research range from the manufacture of bananas engineered to contain vaccines (to eliminate the challenge of cold vaccine storage in developing countries) to coffee plants that have been altered to "switch off" caffeine before the beans even start growing.
Genetic engineering is controversial and has led to many protests regarding the potential of short- and long- term health and environmental risks. Stem-cell research is particularly controversial. Stem cells have traditionally been culled from aborted fetuses or from embryos left behind after successful fertility treatments, or they are produced using cloning technology. Many fear that using stem-cell research to cure genetic disorders or produce body tissues will eventually lead to the process being used to enhance or improve humans, a practice known as positive eugenics, termed by opponents as the "search for the master race." It is feared that altering human genomes may have unknown consequences for future generations that inherit the changes. Some individuals, including James Watson, co-discoverer of DNA's double-helix structure, are not opposed to altering DNA to make human "improvements."
The primary concerns with genetic engineering in plants are that a transferred gene could migrate unintentionally via pollen scattering from a transgenic plant to a related species and alter the ecosystem, or that a plant designed to kill a particular pest could end up killing beneficial insects like bees and butterflies. Transgenic plants could also interbreed with weeds, producing weeds resistant to herbicides. Allergens from one food crop, such as peanuts, can be transferred to another through genetic engineering. Animal-rights groups have argued that genetically engineered fish may cause problems if they interbreed with unaltered fish, which may change the characteristics of wild fish. The use of bovine growth hormone to increase dairy-cow milk production is also controversial, with critics questioning its safety for both cows and the humans who consume the milk.
The advances in genetic engineering require health care practitioners to consider their responsibilities in handling genetic information. As genetics advances are incorporated into tools for primary health care delivery, the use of genetic assessment testing will expand in medical practice. Health care practitioners, including nurses and allied-health professionals, will need a functional understanding of the potential ethical, legal, and social issues involved with such tests; special attention must be paid to disclosures for informed consent, and medicalrecord confidentiality. A statement on the Scope and Standards of Genetics Clinical Nursing Practice has been published by the American Nurses Association to guide nurses in their practice of genetic-based health care.
Cloninghe production of an organism that is genetically identical to its parent.
Deoxyribonucleic acid (DNA)he genetic material of all cellular organisms and most viruses. DNA carries the information needed to direct proteins. Each molecule of DNA consists of two twisted strands, called a double helix.
Eugenics practice involving use of genetic principles to "improve" humankind.
Genehe basic unit of hereditary traits found in the cells of all living organisms, from bacteria to humans. Genes determine the physical characteristics that an organism inherits, such as hair and eye color.
Human Genome Projectn international scientific collaboration that seeks to identify and clarify the entire human genetic blueprint.
Protein molecule made of a sequence of amino acids. Proteins are the most common organic molecules in living organisms and among the most complex.
Recombinant DNANA that has been altered by joining genetic material from two different sources. It usually involves putting a gene from one organism into the genome of a different organism.
Stem cellshe undifferentiated cells from which specialized embryonic cells develop.
Anderson, G., R. B. Monsen, C. A. Prows, S. Tinley, J. Jenkins. "Preparing the Nursing Profession for Participation in a Genetic Paradigm in Health Care." Journal of Nursing Outlook (2000): 48, 23-27.
Collins, F. "Medical and Societal Consequences of the Human Genome Project." New England Journal of Medicine 341, no. 1 (1999): 28-37.
Lea, D. "A New World View of Genetics Service Models." Online Journal of Issues in Nursing 5, no. 3 (2000). Available at <<a href="http://www.nursingworld.org/ojin/topic13/tpc13_6.htm">http://www.nursingworld.org/ojin/topic13/tpc13_6.htm>.
The American Society of Human Genetics. 9650 Rockville Pike, Bethesda, MD 20814-3998. (301)571-1825. <<a href="http://www.faseb.org/genetics/ashg/ashgmenu.htm">http://www.faseb.org/genetics/ashg/ashgmenu.htm>.
The International Society of Nurses in Genetics. <<a href="http://nursing.creighton.edu/isong">http://nursing.creighton.edu/isong>.
National Coalition for Health Professional Education in Genetics. (410) 583-0600. <<a href="http://www.nchpeg.org">http://www.nchpeg.org>.
The Human Genome Project. <<a href="http://www.ornl.gov/hgmis/medicine/medicine.html">http://www.ornl.gov/hgmis/medicine/medicine.html>.
Genetic Engineering (Encyclopedia of Science and Religion)
The term genetic engineering refers to technologies that modify genes. Unlike selective breeding, which merely chooses traits that are already found in nature, genetic engineering acts directly on the genetic material itself in order to alter an organism's traits. Genetic engineering is the cornerstone of modern biotechnology, and through it human beings have the power to modify the molecular basis of all forms of life.
A brief history
The concept of genetic engineering emerged in the 1960s and was first realized in the 1970s. Its development depended upon a century of advances in science, beginning in the 1860s with Gregor Mendel's discovery of the existence of factors that govern inheritance. In the 1940s, it was learned that these factors, now called genes, are composed of a complex molecule, deoxyribonucleic acid or DNA. In 1953, Francis Crick and James Watson described the structure of DNA as the famous double helix along which are found pairs of chemicals. Soon it was learned that the sequence of these chemicals, known as bases, carries information that instructs the cell how to make proteins that are essential to the structure and function of the cell.
By the 1960s, it was becoming clear that scientists would soon learn how to manipulate this chemical information and thereby engineer genes. In the ensuing decades, various techniques for manipulating DNA have been developed, beginning in the early 1970s with the discovery of the use of restriction enzymes, which exist in nature and which cut and join strands of DNA at precise locations. This allows scientists to cut and splice DNA. A later discovery called polymerase chain reaction (PCR) made it possible for researchers to produce huge quantities of specific DNA sequences. Further advances in the use of computers to decode, store, and manipulate DNA means that researchers can discover and modify DNA on a broad scale and with considerable precision.
Genetic engineering uses various methods in pursuit of many goals. One method is to transfer a gene from one organism to another. For instance a human gene may be transferred to a microorganism in order to develop a new strain of microorganism that will produce a human protein, such as insulin, for pharmaceutical purposes. Much of the insulin used by diabetics comes from this process. It is possible in fact to transfer many genes into an organism by packaging them together as a kind of artificial chromosome, sometimes called a gene cassette. Plants, too, are genetically engineered to produce pharmaceutical products, to enhance their protein value as foods, to allow them to grow with less reliance on pesticides or fertilizers, to resist freezing or spoiling, to enhance flavor, or perhaps to grow in seawater. Another method is to incapacitate a particular gene by deliberately causing it to mutate and shut itself down. For instance if scientists know that an impaired human gene is linked to a disease such as cancer, they will find the corresponding gene in laboratory rats, shut it down, and create a strain of rats with this gene knocked out, and therefore with a high likelihood for cancer, in order to have animals on which to test possible therapies.
In human beings, scientists have attempted to modify or replace genes in some of the cells of patients' bodies in order to treat diseases with genetic basis. This strategy, called gene therapy, began in 1990 with mixed success. In time it will likely become widely used to treat a variety of diseases. Still another method is to modify a tiny portion of the genene or two bases of DNAy constructing a special small molecule that can trigger what is called a mismatch repair. Ordinarily the body corrects for the mutations that occur naturally inside the body all the time, and scientists are learning how to exploit the body's own repair mechanisms to correct mutations that may have been inherited. These strategies used so far on human beings differ sharply from what scientists are attempting to do with other animals. In human beings, researchers are attempting to change the genes only in selected cells that are affected by the disease. In animals, however, the modifications affect every cell and are passed on to future generations. That strategy, often called germline modification, has been proposed for use on human beings but remains controversial from the standpoint of safety.
From the time genetic engineering was first considered in the 1960s, religious scholars and institutions have commented on its value and limits. Often scientists themselves, not to mention science journalists, report on developments in genetics in religious terms, speaking of DNA as the mystery of life or the human genome as the holy grail of biology. Not surprisingly, the general public sometimes responded to these developments with religious fervor, sometimes in favor of them, but often opposed to developments that people saw as, for instance, playing God.
One concern of special importance to many religious scholars and leaders has been the use of the system of patenting, by which governments give exclusive rights for a time to inventors, to protect developments in genetics. Particularly troubling has been the granting of patents to gene sequence information. Many have argued that knowledge of genes is discovery, not invention, and should not be eligible for patent protection. Many have also argued that granting biological patents amounts to patenting life, therefore making life a mere commodity. Other religious scholars recognize that patenting, while not perfect, is essential to the financial development of the full potential of genetic engineering, and that opposition to patenting is tantamount to opposing the benefits of research.
Beyond these general concerns, many religious scholars and organizations have considered developments in genetic engineering on a case-by-case basis. For instance, many religious organizations have responded to the use of genetic engineering to modify food by recognizing its potential for increasing the quality and quantity of food, but with cautions having to do with the viability of small farms, global inequities, the power of corporations in view of intellectual property rights, and the right of consumers to know what they are eating. Similarly, religious scholars have raised concerns, but generally have not objected categorically, to genetic engineering of animals. Of special concern is the prospect of herds of genetically identical livestock becoming vulnerable to disease, or to the use of genetic engineering to create strains of animals whose sole purpose is to suffer a disease for the benefit of medical research.
Quite understandably, human applications evoke the most intense religious responses. Religious responses to the use of genetic engineering for pharmaceutical purposes have been positive, with concerns limited to patenting, to the high costs of medicines, and to the need for socially just patterns of distribution. Furthermore, almost without exception, human gene therapy has met with approval not just by the public, but by religious institutions and scholars, who assess it morally as an extension of traditional medicine. Issues of safety remain, and many are concerned that the technique, when shown to be beneficial, will not be justly distributed.
The greatest concern, however, is that the technique will not be limited in its application to therapy but will be used for enhancement of human health and possibly of traits that are unrelated to health. Those who voice this concern point not just to cosmetic surgery and to performance enhancing drugs in sports but to the use of mood-altering pharmaceutical products, such as the drugs known as selective serotonin reuptake inhibitors (SSRIs). Evidence exists that people request these drugs not to treat anxiety or depression but to improve their mood and thus their performance in life. If that is true, some argue, how much more will people request gene modification that enhances their state of being and their performance. As of 2002, it is not at all clear which human traits will become susceptible to enhancement by genetic engineering. Height, most definitely, will be modifiable, but perhaps mental and emotional traits may be modifiable too. The concern here is the lack clarity about the distinction between therapy and enhancement, and thus the lack any publicly credible way to prevent those with economic or political means from acquiring new ways to improve themselves to the competitive disadvantage of others.
Sometime in the twenty-first century, many believe, humans will learn how to modify the genes of their offspring. Such germline modification, as it is usually called, is already done in other mammals, although not reliably. Many technical obstacles lie ahead, but learning to do this in human beings has a strong attraction, for some, in the promise that a family might be freed of a genetic disease that has afflicted it for generations. Other techniques, such as testing an embryo for disease before it is implanted, will probably achieve the same result at less cost and risk. If so, it may turn out that the real advantage of germline modification is not to eliminate disease but to improve the next generation, perhaps by enhancing resistance to disease or by producing other traits. The prospect of children born with such enhancement, often referred to as designer babies, is widely opposed by the general public, secular scholars, and religious leaders, even though most analysts concede that it probably cannot be prevented.
Religious objections to germline modification are that the resulting children will enter the world as objects, engineered according to the will of their designers and not as persons who emerge from the love of their parents. The intrusion of technology perverts the relationship between parent and child, difficult under any circumstance, but all the more so if parents can use technology to express their desires for the kind of child they want to have. Others believe that designed children will face impossible expectations in achieving that for which they are designed, and that they will likely resist their makers' intentions.
See also BIOTECHNOLOGY; CLONING; DNA; EUGENICS; GENE PATENTING; GENE THERAPY; GENETICALLY MODIFIED ORGANISMS; GENETICS; HUMAN GENOME PROJECT; PLAYING GOD; STEM CELL RESEARCH
Bruce, Donald, and Bruce, Ann, eds. Engineering Genesis: The Ethics of Genetic Engineering in Non-Human Species. London: Earthscan, 1998
Chapman, Audrey R. Perspectives on Genetic Patenting: Religion, Science, and Industry in Dialogue. Washington, D.C.: American Association for the Advancement of Science, 1999.
Chapman, Audrey R. Unprecedented Choices: Religious Ethics at the Frontiers of Genetic Science. Minneapolis, Minn.: Fortress Press, 1999
Chapman, Audrey R., and Frankel, Mark S. Human Inheritable Genetic Modifications: Assessing Scientific, Ethical, Religious, and Policy Issues. Washington, D.C.: American Association for the Advancement of Science, 2000. Available at http://www.aaas.org/spp/dspp/sfrl/germline/report.pdf
Cole-Turner, Ronald. The New Genesis: Theology and the Genetic Revolution. Louisville, Ky.: Westminster John Knox Press, 1993.
Cole-Turner, Ronald. Beyond Cloning: Religion and the Remaking of Humanity. Harrisburg, Pa.: Trinity Press International, 2001.
Evans, John H. Playing God? Human Genetic Engineering and the Rationalization of Public Bioethical Debate. Chicago: University of Chicago Press, 2002
Hanson, Mark J., ed. Claiming Power over Life: Religion and Biotechnology Policy. Washington, D.C.: Georgetown University Press, 2001.
Fletcher, Joseph. The Ethics of Genetic Control: Ending Reproductive Roulette. Garden City, N.Y.: Doubleday, 1974
Kilner, John F.; Pentz, Rebecca D.; and Young, Frank E., eds. Genetic Ethics: Do the Ends Justify the Genes? Grand Rapids, Mich.: Eerdmans, 1997.
Mackler, Aaron, ed. Life and Death Responsibilities in Jewish Biomedical Ethics. New York: Louis Finkelstein Institute and Jewish Theological Seminary of America, 2000
National Council of Churches, Panel on Bioethical Concerns. Genetic Engineering: Social and Ethical Consequences. New York: Pilgrim Press, 1984.
Peters, Ted. Playing God: Genetic Determinism and Human Freedom. New York: Routledge, 1997.
Peters, Ted, ed. Genetics: Issues of Social Justice. Cleveland, Ohio: Pilgrim Press, 1998.
Peterson, James C. Genetic Turning Points: The Ethics of Human Genetic Intervention. Grand Rapids, Mich.: Eerdmans, 2001.
Rahner, Karl. "The Problem of Genetic Manipulation." In Theological Investigations, Vol. 9, trans. G. Harrison. New York: Seabury, 1966.
Rahner, Karl. "The Experiment with Man: Theological Observations on Man's Self-Manipulation." In Theological Investigations, Vol. 9, trans. G. Harrison. New York: Seabury, 1966.
Ramsey, Paul. Fabricated Man: The Ethics of Genetic Control. New Haven, Conn.: Yale University Press, 1970.
Shinn, Roger Lincoln. The New Genetics: Challenges for Science, Faith and Politics. Wakefield, R.I., and London: Moyer Bell, 1996.
Willer, Roger A., ed. Genetic Testing and Screening: Critical Engagement at the Intersection of Faith and Science. Minneapolis, Minn.: Kirk House, 1998.
World Council of Churches, Church and Society. Manipulating Life: Ethical Issues in Genetic Engineering. Geneva: World Council of Churches, 1982.
World Council of Churches, Church and Society. Biotechnology: Its Challenges to the Churches and the World. Geneva: World Council of Churches, 1989.
Genetic Engineering (Encyclopedia of Food & Culture)
GENETIC ENGINEERING. Genetic engineering involves the directed alteration of an organism's DNA (deoxyribonucleic acid)hat is, its genetic material. This technology has been applied to microbes, plants, and animals, and consequently used to modify foods, animal feedstuffs, and food-processing reagents.
Domestication and improvement of plants and animals for agriculture initially relied on identification of individuals with desirable characteristics from among natural populations. Applying knowledge of genetics to the breeding of plants and animals resulted in more rapid progress and remains vitally important to agricultural development. Traditional breeding, however, is constrained by the boundaries of sexual compatibility, which limits the choice of parents that can be used as sources of genes and traits to improve a specific crop or animal to those that can produce progeny through sexual reproduction. Genetic engineering expands the source of genes that can be used to modify the characteristics of plants and animals.
Technology of Genetic Engineering
Genetic engineering requires three fundamental technologies: the ability to isolate and modify the DNA of specific individual genes; an understanding of the mechanisms that regulate how genes function and how these can be manipulated; and the capacity to transfer genes into an organism. These have all been developed following the discovery of the structure of DNA in 1953. Genetic engineering of microbes was first reported in 1973, followed in the next decade by similar achievements in plants and animals. Because DNA is the genetic material in all organisms, genes for genetic engineering can be taken from any source, or even synthesized. Modification of genes may be necessary, particularly in regions that control how they operate, in order for the genes to function effectively in the recipient organism. Agrobacterium tumefaciens, a bacterium that transfers DNA into plant cells as part of its normal life cycle, is used commonly to transfer genes into plants, although other methods such as the "gene gun" also have been developed. Genetically engineered plants are technically "transgenic organisms," as they contain transferred genes. However, they are frequently referred to as "genetically modified organisms," or GMOs, and the products derived from them are described as "genetically modified," or GM foods. These terms can be confusing, as essentially all cultivated plants have been genetically modified through breeding and selectionor example, the many varieties of cultivated onions possess numerous qualities that distinguish them from each other and especially from the wild onions from which they originated.
Application of Genetic Engineering in Agriculture
The first genetically engineered crops were planted on a large scale in 1996. By 2001 more than fifty million hectares were planted worldwide with transgenic crops. The first generation of these crops has been altered in ways that improve the efficiency of crop production by modifying the tolerance of plants to herbicides and insect pests. Broad-spectrum herbicides are able to kill almost all plants. A prerequisite for using chemicals to control weeds in a crop is that the crop itself must be resistant to the herbicide. Genetic engineering has been used to develop plants (specifically soybean, canola, corn, and cotton) with resistance to two broad-spectrum herbicides, glyphosate and glufosinate, which are sold under the trademarks Roundup and Liberty, respectively. Glyphosate-tolerant soybeans have been adopted rapidly in some countries, notably the United States and Argentina, and accounted for approximately 46 percent of the soybean acreage worldwide in 2001. Herbicide use has not declined in these crops but the specific herbicides that are used have changed.
Insect pests can damage crops during the growing season and also after harvest. A variety of methods, including cultural practices and insecticides, are used to control insect damage. Genetic engineering has provided novel approaches to this problem. The bacterium Bacillus thuringiensis (Bt) produces proteins that are toxic to some types of insects, and Bt spores have been used as insecticides for decades. Genes encoding Bt toxin proteins have been isolated, modified so they function in plants, and transferred into crop plants including corn, potato, and cotton. These engineered Bt crops are more resistant to such insects as the European corn borer, Colorado potato beetle, and cotton bollworm than are their nonengineered counterparts. The introduction of Bt cotton has resulted in reduced use of insecticides on this crop in some regions of the United States. Growers of Bt crops are required to plant a portion of their acreage with varieties that do not carry the Bt gene, in an effort to delay the development of insect populations with resistance to Bt toxins.
The Flavr Savr tomato, developed in the 1980s by Calgene, a biotechnology company in California, was the first food produced from a genetically engineered plant. These tomatoes ripened more slowly and had an extended shelf life. However, for a number of reasonsncluding production problems and consumer skepticismhis product was not a commercial success and was withdrawn in 1996, after less than three years on the market. Melons and raspberries have also been engineered to have delayed ripening but have not been produced commercially. Transgenic papayas with resistance to ring spot virus also have been developed. These were grown successfully in Hawaii, where the papaya industry was devastated by this debilitating disease. A similar approach was used to produce virus-resistant summer squash and against other viruses affecting a wide variety of foodstuffs.
The first generation of transgenic crops for the most part were designed to improve the efficiency of crop production, an ongoing objective for genetic engineers. Additionally, the techniques of genetic engineering can be used to alter the nutritional composition of foods. The transfer into rice of three genes that function to produce beta-carotene in the seed resulted in "golden rice." Once consumed, beta-carotene can be converted to vitamin A, the degree of this conversion being dependent upon a number of factors that relate to the source of the beta-carotene, the diet, and the individual consumer. In less-developed countries, vitamin A deficiency is widespread among those with a restricted diet, and is responsible for increased mortality and blindness in children. Although the efficacy of transgenic rice in reducing disease has not been established, it demonstrates the potential use of genetic engineering for nutritional enhancement in many crops. Other applications of genetic engineering of animal and human foods include removing allergens from foods such as peanuts, increasing the level of essential vitamins and nutrients in foods, and producing foods possessed of vaccines and other beneficial compounds.
Genetically engineered microbes also are used to produce proteins for food processing. Chymosin (or rennin), an enzyme used in cheese production, traditionally is obtained from the stomach of veal calves. However, the gene encoding this enzyme was transferred into microbes, and the enzyme now can be produced in bulk by purifying it from large microbe cultures. Chymosin prepared from transgenic microbes has more predictable properties than the animal product and is used to produce more than fifty percent of hard cheeses in the United States. Other enzymes used in food processing are produced by similar methods. For example, bovine growth hormone (BGH) is produced in large quantities from transgenic microbes and is given to cows to increase milk production.
Regulation of Genetic Engineering
In the United States, three federal agenciesood and Drug Administration (FDA), Environmental Protection Agency (EPA), and Department of Agriculture (USDA) re involved in regulating transgenic crops. Similar systems are in place in other countries as well. Companies that have developed this technology generally are supportive of the current regulatory framework. Nevertheless, the development of transgenic crops and the introduction of foods that contain products from these plants in the 1990s generated tremendous controversy, notably in Europe. Proponents of genetic engineering have argued that the addition of one or two well-characterized genes into crop plants that have a history of safe use is unlikely to affect materially the properties of these plants. Opponents suggest that this technology has not been tested adequately and the public should not be exposed to unknown and unnecessary food-based risks.
Safety concerns include the possibility that this technology will reduce the nutritional content of foods and introduce novel allergens or other toxins into foods. Opponents have sought more extensive testing and mandatory labeling of products that contain genetically engineered foods so that consumers can choose whether or not to eat such items. The impact of transgenic crops on the environment also has been questioned. Pests are likely to develop resistance to toxins produced by transgenic plants, raising doubts about the sustainability of this approach. However, transgenic technology also has the potential to reduce the use of chemical pesticides for crop production, which most regard as a positive development. Transfer of genes from engineered crops to other plants might also occuror example, making weeds resistant to a specific herbicide or expanding the range of a plant so that it can grow in new locations.
This new technology also brings forth social, economic, and ethical issues, many of which are reflected by a wide political debate. One subject of concern is that most of the technology enabling genetic engineering of crop plants is controlled by a small number of companies. Much of this control is achieved through ownership of intellectual property, such as patents on genes, methods to produce transgenic plants, and the plant material that is the basis for crop improvement. Companies that manage agricultural inputs, such as seeds, pesticides, and fertilizers, as well as food processing and retail operations, function increasingly on a global scale. Opponents of globalization have criticized genetic engineering as one factor that is contributing to this trend and have expressed concern that both farmers and consumers will have limited choice in who supplies their needs. Opposition to genetic engineering also has come from religious groups who believe that tampering with genes in this way is unnaturalhat is, inconsistent with the divine domain of naturend should not be allowed.
Development of methods to genetically modify plants that extend beyond the limits of normal sexual reproduction has the potential to change many aspects of food production. Some of the first generations of products of this technology were adopted readily by most farmers but, as with other new technologies, there are many opponents. If this technology eventually receives widespread acceptance, it is likely that genetically engineered products will be found in almost everything that humans and domesticated animals eat.
See also Additives; Agronomy; Biotechnology; High-Technology Farming; History of Food Production.
Charles, Daniel. Lords of the Harvest: Biotech, Big Money, and the Future of Food. Cambridge, Mass.: Perseus Publishing, 2001. A history of the development of agricultural biotechnology and genetically engineered foods.
Colorado State University. Transgenic Crops: An Introduction and Resource Guide. Available at http://www.colostate.edu/programs/lifesciences/TransgenicCr...
Ervin, David, Sandra Batie, Rick Welsh, Chantal Carpentier, Jacqueline Fern, Nessa Richman, and Mary Schulz. Transgenic Crops: An Environmental Assessment. Morrilton, Ark.: Winrock International, 2000. Available at http://www.winrock.org/Transgenic.pdf
Nuffield Council on Bioethics. Genetically Modified Crops: The Ethical and Social Issues. London: Nuffield Council on Bioethics, 1999. A report from the United Kingdom that addresses consumer issues.
Pew Initiative on Food and Biotechnology. Harvest on the Horizon: Future Uses of Agricultural Biotechnology. Washington D.C.: Pew Initiative, 2001. Available at http://pewagbiotech.org/research/harvest/
Watson, James, Michael Gilman, Jan Witkowski, and Mark Zoller. Recombinant DNA. 2nd ed. New York: W. H. Freeman, 1992. A detailed description of the science behind genetic engineering.