Genetically Modified Foods
A genetically modified (GM) food is a plant that has a genetic change in each of its cells that a researcher has introduced. The modification may add a gene from a different species and thereby create a transgenic plant, or it may overexpress or silence a preexisting plant gene. Overexpression is accomplished by altering the promoter region of a gene, which controls how rapidly and in which cells the encoded protein is synthesized, thus directing a plant to manufacture more of a natural product. Conversely, a gene may be "silenced" (directed not to synthesize a protein) through the use of antisense technology, which applies a complementary nucleic acid to messenger RNA, halting expression of the encoded protein.
Genetic Modification in Animals and Plants
Animals have not yet been genetically modified to provide foods. Transgenic 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.
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