Bt toxin in cotton plants is present in the form of:

The correct answer is Option (3) → Inactive protoxin

The soil bacterium Bacillus thuringiensis makes protein crystals that hold an insecticidal protein, the Bt toxin. The toxin is made as an inactive protoxin. When an insect eats it, the alkaline pH of the insect gut dissolves the crystals and changes the protoxin into the active toxin. The active toxin makes pores in the cells of the gut wall. The cells swell and burst, and the insect dies. In Bt cotton the cry gene makes the toxin in the same inactive form, so the plant itself is not harmed.

(1) Lipid — Incorrect. The Bt toxin is a protein, not a fat.

(2) RNA — Incorrect. The cry gene is a stretch of DNA, and the toxin it codes for is a protein. RNA is not the toxin.

(3) Inactive protoxin — Correct. The protein is inactive until the alkaline gut of the insect activates it.

(4) Active toxin — Incorrect. The toxin becomes active only inside the insect gut, after it is eaten.

NCERT Extract:
Biotechnological Applications in Agriculture – …