Explanation

Specific Bt toxin genes obtained from bacteria Bacillus thuringiensis are used in several crop plants. The toxin is coded by a gene called cry, which is of various types. For example, proteins encoded by the genes cry I Ac and cry II Ab controls the cotton bollworms and that of cry I Ab controls corn borer. Bt toxin are initially inactive protoxins but after ingestion by the insects their inactive toxins become active due to the alkaline pH of the gut, which solublise the crystals