One of the applications of biotechnology is the production of insect resistant crop plants." Justify the statement with reference to Bt-cotton.

Explanation

(a) Bt-cotton :
`cdot` Bacillus thuringiensis produces crystal protein called Cry proteins which are toxic to larve of insects like tobacco bud worm , army worm , beetles and mosquitoes .
`cdot` Cry proteins exist as inactive protoxins and get converted into active toxin when ingested by the insect , as the alkaline pH of the gut solubilises the crystals.
`cdot`The activated toxin binds to the surface of epithelial cells of midgut and creates pores.
`cdot` This causes swelling and lysis of cells leading to the death of the insect (larva).
`cdot` The genes (cry genes ) encoding this protein are isolated from the bacterium and incorporated into several crop plants like cotton , tomato , corn , rice , soybean , etc .
`cdot` The proteins encoded by the following cry genes control the corresponding pests .
`ast` Cry I AC and Cry II Ab control cotton bollworms .
`ast` Cry I Ab controls corn borer .
`ast` Cry III Ab controls colarado potato beetle.
`ast` Cry III Bb controls corn rootworm .