Ques. 1AIPMT 2009
What is true about Bt toxin?
- The activated toxin enters the ovaries of the pest to sterilise it and thus prevent its multiplication.
- Bt protein exists as active toxin in the Bacillus
- The concerned Bacillus has antitoxins
- The inactive protoxin gets converted into active form in the insect gut
Answer
(4) The inactive protoxin gets converted into active form in the insect gut
Solution
As per NCERT, Bacillus thuringiensis forms protein crystals containing a toxic insecticidal protein.
The Bt toxin protein exists as an inactive protoxin in the bacterium, it does not kill the Bacillus itself.
Once an insect ingests it, the alkaline pH of the gut solubilises the crystals and the inactive protoxin is converted into the active toxin.
The active toxin binds to the surface of midgut epithelial cells and creates pores that cause swelling and lysis, and finally the death of the insect.
Answer: (4)