**3.4 Production of insect resistant Bt cotton using genetic engineering**

The bacteria *Bacillus thuringiensis* synthesize certain proteins with the ability to kill insects like dipterans and lepidopterans. This toxin was termed Bt toxin which remains inactivate, but when engulfed it gets activated due to the alkaline pH of the gut. The insects engulfing it eventually die. Through genetic engineering the genes responsible for production of Bt toxin were isolated and were used in crops like cotton to make it pest resistant. The toxin responsible for killing the pest was coded using *cry* gene. The Bt cotton was resistant against budworms, beetles, mosquitoes, and flies [22].
