Bt cotton is a transgenic plant that is insect resistant. It contains Bt toxin genes (cryIAc and cryIIAb) derived from soil bacterium Bacillus thuringiensis. These genes produce a toxic insecticidal protein which, when ingested by lepidopteran insects, cause their death. This toxin exists as inactive protoxins. But, once an insect ingests the crystals, it is converted into an active form of toxin due to the alkaline pH of the alimentary canal. Activated toxin creates pores in the epithelial cells of midgut of insects that causes lysis, swelling and eventually death.