Genetic Modification in Animals and Plants

Animals have not yet been genetically modified to provide foods. Trans-genic animals can, however, produce certain pharmaceuticals, but this approach is still experimental. One possible future use of transgenic animals is to create herds of cattle or sheep that are genetically resistant to developing transmissible spongiform encephalopathies, such as scrapie in sheep and "mad cow disease" in cattle.

Genetic modification in plants produces the same types of changes that result from traditional agricultural techniques, such as controlled breeding. However, genetic modification alters one gene at a time in a controlled manner, and typically has faster results than breeding plants with particular combinations of traits. With standard breeding techniques, it may take a generation to introduce, or remove, a single gene. Breeding a polygenic trait (a trait that involves more than one gene) into apples, which have a generation time of four years, could take two decades or longer.

GM traits that have already been introduced into plants include resistance to insects, insecticides, and herbicides; larger fruits; salt tolerance; slowed ripening; additional nutrients; easier processing; insecticide production; and the ability to take its own nitrogen from the air, lowering reliance on fertilizer. Specific products of genetic manipulation include insect-resistant corn, frost-resistant strawberries, rice that makes beta-carotene (a

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