One of the applications of biotechnology is to get Pest resistance plants. Justify the statement with reference to Bt.Cotton.

Explanation

Some strains of Bacillus thuringiensis produce protein crystals, that kill insects Lepidopterans, coleopterans and Dipterans. Protein crystals formed during certain phase of their growth.
The cry gene, cry IAC and Cry IIA6 from B.thuringenesis coding for the toxins are transferred to cotton plants bollworms.
Bt cotton plants express the Bt toxin gene by producing foxin that provides insect resistance.
Bt toxin protein exists as an inactive prototoxins. Insect ingest the inactive toxin, converts to active toxin at alkaline pH of gut of inseçt which solubilise the crystals.
Toxin binols to surface of midgut epithelial cells create porus that cause cell swelling and lysis and eventually cause death of insect.