CUET · BIOLOGY · PYQ PAPER 2025

Which one of the followings is not a feature of insecticidal protein crystals formed by Bacillus thuringiensis: -

A When formed they exist as inactive protoxin.
B They are converted into an active form of toxin in the alkaline pH of the gut, which solubilize the crystals.
C They are effective against certain insects such as lepidopterans, coleopterans and dipterans.
D The activated toxin does not bind the surface of midgut epithelial cells which leads to pore formation, cell swelling and lysis.

Verified Solution

Answer & Solution

Correct Answer

(D) The activated toxin does not bind the surface of midgut epithelial cells which leads to pore formation, cell swelling and lysis.

Step-by-step Solution

Detailed explanation

The activated toxin does not bind the surface of midgut epithelial cells which leads to pore formation, cell swelling and lysis.

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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List - I	List - II
(A) Salmonella typhimurium	(I) Thermostable DNA polymerase
(B) Thermus aquaticus	(II) First recombinant DNA
(C) Bacteriophage	(III) Cry protein
(D) Bacillus thuringiensis	(IV) Cloning vector