An insect ingests the inactive toxin, it is converted into an active form of toxin due to -
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Alkaline pH of the gut
Option (1) Acidic pH of the gut — Incorrect. The insect gut is alkaline, not acidic. The toxin crystals dissolve only in an alkaline medium.
Option (2) Alkaline pH of the gut — Correct. The Bt toxin stays as an inactive protoxin inside the bacterium. In the alkaline gut of the insect the crystals dissolve, and the protoxin becomes the active toxin. The toxin then makes pores in the midgut cells, which swell and burst, and the insect dies.
Option (3) Neutral pH of the gut — Incorrect. At a neutral pH the protoxin stays inactive. That is also why the toxin does not harm the bacterium that makes it.
Option (4) Low pH of the gut — Incorrect. A low pH means an acidic medium, so this is Option (1) in other words. The activation needs a high (alkaline) pH.
Note: A similar question was also asked in CUET (UG) 2022 on 30-08-2022 (Slot 2) and on 16-07-2022 (Slot 1).
NCERT Extract:
Biotechnological Applications in Agriculture – …
