USDA Economic Research Service July 20, 1999
"For thousands of years, genes have been manipulated empirically by plant and animal breeders who monitor their effects on specific characteristics or traits of the organism to improve productivity, quality, or performance. A basic understanding of how traits are transmitted was formed by Gregor Mendel in the 19th century. His experiments and concepts showed that traits were controlled by units of heredity called genes. Extensions of his work led to the formation of applied genetics and breeding programs. The physical and chemical nature of genes remained unknown until the 1950s when James Watson and Francis Crick discovered that genes consist of a chemical known as DNA (Deoxyribonucleic acid). DNA contains the information to control the synthesis of enzymes and other proteins that perform the basic metabolic processes of all cells. Each gene is a specific DNA sequence, and more than 100,000 different genes are found in a higher plant or animal species. This total set of genes for an organism (referred to as the nuclear genome) is organized into chromosomes within the cell nucleus. The process by which a multicellular organism develops from a single cell through an embryo stage into an adult is ultimately controlled in the genetic information of the cell and by interaction of genes and gene products with environmental factors." (Vodkin, L.O. "Jumping Genes that Control Plant Traits." In Research for Tomorrow, 1986 Yearbook of Agriculture. USDA, Washington, DC. 1987).
Biotechnology is broadly defined as the use of biological processes of microbes, and of plants or animal cells for the benefit of humans.
Bt crops are genetically engineered to carry the gene from the soil bacterium Bacillus thuringiensis. The bacteria produces a protein that is toxic when ingested by certain Lepidopteran insects. Crops containing the Bt gene are able to produce this toxin, thereby providing protection throughout the entire plant.
Bt cotton is genetically engineered to control tobacco budworms, bollworms, and pink bollworms.
Bt corn is genetically engineered to provide protection against the European corn borer.
Cell is the smallest structural unit of living organisms that is able to grow and reproduce independently.
Genetic engineering, very broadly, is a technique used to alter or move genetic material (genes) of living cells. Narrower definitions are used by agencies that regulate genetically modified organisms (GMO's). In the U.S., under guidelines issued by USDA's Animal and Plant Health Inspection Service, genetic engineering is defined as the genetic modification of organisms by recombinant DNA techniques (7CFR340: 340.1), while definitions used in Europe are somewhat broader.
Gene stacking involves combining traits (e.g. herbicide tolerance and insect resistance) in seed.
Herbicide-tolerant crops were developed to survive certain herbicides that previously would have destroyed the crop along with the targeted weeds, and allow farmers to use them as postemergent herbicides, providing an effective weed control. The most common herbicide-tolerant crops (cotton, corn, soybeans, and canola) are Roundup Ready (RR) crops resistant to glyphosate, a herbicide effective on many species of grasses, broadleaf weeds, and sedges. Other genetically modified herbicide-tolerant crops include Liberty Link (LL) corn resistant to glufosinate-ammonium, and BXN cotton resistant to bromoxynil.
Plant breeding is use of techniques involving crossing plants to produce varieties with particular characteristics (traits) which are carried in the genes of the plants and passed on to future generations.
Transgenic plants result from the insertion of genetic material from another organism so that the plant will exhibit a desired trait. Recombinant DNA techniques (DNA formed by combining segments of DNA from different organisms) are usually used.
Contact: Kathryn Lipton
Updated: August 5, 1999
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