Question

Assertion :In $Bt$-cotton, $B.$ $thuringiensis$ produces a toxic insecticidal crystalline protein which destroys bollworms. Reason: $B.$ thuringiensis produces this toxic protein in an inactive form, but when an insect ingests this inactive protein, it is converted into an active form of toxin due to the alkaline pH of the gut which solubilises the crystals, which is responsible for the death of bollworm.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

Answer: (D)

Bt cotton is created using the bacterium Bacillus thuringiensis. This bacterium produces protein $cry$ that contains a toxic insecticidal protein. The gene that produces this toxic protein, is incorporated in cotton and Bt cotton is produced. Hence, assertion is incorrect.

Bt toxin doesn't kill the bacterium Bacillus thuringiensis because it is formed in an inactive form. When the insect ingests the inactive toxin, it gets exposed to the alkaline pH of the gut which solubilize the crystal and it is converted into the active form. The activated toxin binds to the midgut of epithelial cells and creates pores and causes swelling and lysis and eventually causes the death of the insect. Hence, the reason is correct.

So, the correct answer is D.