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Biotechnology and its Applications, , Genetically Engineered Crops, , « Genetically engineered crops have desirable genes (as of insect/pest, resistance, giving better yield) incorporated in them., « Genetically modified crops have, © more tolerance to abiotic stresses such as cold, drought, salinity,, heat, etc., oc insect/pest resistance, o reduced post-harvest losses, o efficient mineral usage by plants, eo enhanced nutritional value (e.g., Vitamin A rich rice), , Bt Cotton, , e Bacillus thuringiensis is a bacterium that produces proteins to kill, certain insects such as lepidopterans (armyworm), coleopterans, (beetles), and dipterans (flies/ mosquitoes). B. thuringiensis produces, a protein crystal containing a toxic protein (inactivated state)., , alkaline pH, , « Inactivated toxin Activated toxin (gut of insect), , « Activated toxin binds to the epithelial cells in the midgut of insect and, creates pores that cause lyses and swelling and eventually death of, insect., , « This toxin is encoded by a gene called Cry in the bacterium. Genes, encoded by Cry IAc and Cry II Ab control cotton bollworms and those, encoded by Cry IAb control corn borer., , « Cry genes are introduced into the cotton plants to produce Bt cotton,, which is an insect resistant variety of cotton., , RNA Interference (RNAi), , « RNAi is a method adopted to prevent infestation of roots of tobacco, plants by a nematode Meloidegyne incognitia., e In RNAi, a complementary RNA binds to mRNA to form a ds RNA,