Name the sources and the types of cry genes isolate from it for incorporation into crops by biotechnologists. Explain hoe these genes have brought beneficial changes in the genetically modified crops.
Bacillus thuringiensis is a bacterium that contains cry genes in its genome. The types of cry genes isolated are Cry IAc, Cry II Ab and Cry IAb. Genes encoded by Cry IAc and Cry II Ab control cotton bollworms and those encoded by Cry IAb control corn borer.
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These genes encode a proteins that acts a toxin to kill certain insects such as lepidopterans (armyworm), coleopterans (beetles), and dipterans (flies/ mosquitoes). These genes produce a protein crystal containing a toxic protein (inactivated state). The inactivated toxin is activated in the gut of insect that by alkaline pH.
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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.