The genes responsible for making Bt cotton plant resistant to boll worms are Cry I Ac and Cry II Ab. These genes from protein crystals during a particular phase of their growth. These crystals contain insecticidal protein. These crystals exist as inactive protoxins but once an insect ingests the inactive toxin it is converted into active form of toxin inside alkaline conditions of gut of insect. This solubilizes the crystals. The active toxin binds to the surface of midgut epithelial cells and create pores that cause cell swelling and lysis and causes death of the insect.
