genetic engineering, the use of various methods to manipulate the DNA (genetic material) of cells to change hereditary traits or produce biological products. The techniques include the use of hybridomas (hybrids of rapidly multiplying cancer cells and of cells that make a desired antibody) to make monoclonal antibodies; gene splicing or recombinant DNA, in which the DNA of a desired gene is inserted into the DNA of a bacterium, which then reproduces itself, yielding more of the desired gene; and polymerase chain reaction, which makes perfect copies of DNA fragments and is used in DNA fingerprinting.

Genetically engineered products include bacteria designed to break down oil slicks and industrial waste products, drugs (human and bovine growth hormones, human insulin, interferon), and plants that are resistant to diseases, insects, and herbicides, that yield fruits or vegetables with desired qualities, or that produce toxins that act as pesticides. Genetic engineering techniques have also been used in the direct genetic alteration of livestock and laboratory animals (see pharming). Genetically engineered products usually require the approval of at least one U.S. government agency, such as the Dept. of Agriculture, the Food and Drug Administration, or the Environmental Protection Agency.

Because genetic engineering involves techniques used to obtain patents on human genes and to create patentable living organisms, it has raised many legal and ethical issues. The safety of releasing into the environment genetically altered organisms that might disrupt ecosystems has also been questioned. The discovery in 2001 of genetically engineered DNA in native Mexican corn varieties made concerns of genetic pollution actual, and led some scientists to worry that the spread of transgenes through cross-pollination could lead to a reduction in genetic diversity in important crops. Imports of genetically modified corn, soybeans, and other crops have been curtailed or limited in some countries, and the vast majority of such crops are grown in just a handful of nations. The Cartagena Protocol on Biosafety, which has been signed by more than 100 nations and took effect in Sept., 2003, requires detailed information on whether and how imported seeds, plants, animals, other organisms, and the like are genetically modified and permits a nation to bar those imports. The United States, however, is not party to the treaty.

Artificial manipulation, modification, and recombination of DNA or other nucleic-acid molecules in order to modify an organism or population of organisms. The term initially meant any of a wide range of techniques for modifying or manipulating organisms through heredity and reproduction. Now the term denotes the narrower field of recombinant-DNA technology, or gene cloning, in which DNA molecules from two or more sources are combined, either within cells or in test tubes, and then inserted into host organisms in which they are able to reproduce. This technique is used to produce new genetic combinations that are of value to science, medicine, agriculture, or industry. Through recombinant-DNA techniques, bacteria have been created that are capable of synthesizing human insulin, human interferon, human growth hormone, a hepatitis-B vaccine, and other medically useful substances. Recombinant-DNA techniques, combined with the development of a technique for producing antibodies in great quantity, have made an impact on medical diagnosis and cancer research. Plants have been genetically adjusted to perform nitrogen fixation and to produce their own pesticides. Bacteria capable of biodegrading oil have been produced for use in oil-spill cleanups. Genetic engineering also introduces the fear of adverse genetic manipulations and their consequences (e.g., antibiotic-resistant bacteria or new strains of disease). Seealso biotechnology, molecular biology.

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