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| 20.1 Traditional Breeding Compared to Biotechnology 1. Genetically modified (GM) foods are becoming widely available. 2. Genetic modification can mean adding a gene, enhancing an organism's own gene, or suppressing an organism's own gene (i.e. antisense technology). Similar Steps, Different Degree of Precision 1. Biotechnology entails genetic alteration of cells, growing multicellular organisms, breeding to obtain individuals that express the desired trait, then field testing. 2. Biotechnology differs from traditional plant breeding in that it is asexual, more precise, faster, and considers one trait at a time. Government Regulation of Crops 1. The U.S. government regulates GM crops the same way it does conventionally bred crops. 2. The FDA evaluates the characteristics of a food, not its origin. 3. The exoneration of Starlink corn was not as widely reported as the initial fears. Biotechnology Provides Different Routes to Solving a Problem 1. Mutant selection regenerates plants from cells grown in herbicide to uncover naturally occurring mutations. 2. Transgenic technology is used to design an herbicide resistant crop. 20.2 Types of Plant ManipulationsAltering Plants at the Gene Level 1. Methods of gene transfer include Ti plasmid in dicots and other methods in monocots. 2. Genes in the nucleus or chloroplast can be manipulated. 3. Many crop species have been engineered to be herbicide or pesticide resistant. 4. The nutritional value of numerous crops has been enhanced. 5. Root systems of engineered plants, through rhizosecretion, can be used for pharmaceutical production. 6. Altering the levels of gene products (promotor enhancement; antisense knockouts) has been widely applied. Altering Plants at the Cellular Level 1. Fusing protoplasts from different types of plants can produce novel variants. 2. An explant grows into an undifferentiated callus. 3. Depending on the culture conditions the callus can yield plantlets, somatic embryos, or somaclonal variants. 20.3 Release of Genetically Modified Organisms to the EnvironmentMicrocosm Experiments 1. Genetically altered plants are tested in microcosms in the laboratory to see how they affect natural ecosystems. Field Tests 1. GM organisms are tested in the field to assess survival, fertility, containment, and interactions with other organisms. Bioremediation 1. Bioremediation is the intentional release of organisms that detoxify certain pollutants. 2. The enzyme-catalyzed detoxification reactions may be a natural part of an organism's biochemistry or may be added transgenically. 3. Organisms used in bioremediation help to detect or detoxify heavy metals, organic wastes, or hidden explosives (land mines) in the environment. 20.4 Economic, Ecological, and Evolutionary Concerns 1. The introduction of GM foods can have economic repercussions because they replace natural sources of substances. 2. Measures must be taken to prevent pollen from transferring transgenes to other species. 3. Herbicide- or pesticide- resistant crops can encourage persistence of this trait in weeds and pests. 4. Use of GM foods varies internationally. Some countries ban GM foods. In the United States the percentage of GM crops produced is growing. 20.5 The Impact of Genomics 1. The benefits and risks of GM crops are still hotly debated. 2. Genomics aids in the identification of useful, as well as harmful, genes in plants. |