Question

Read the following statements regarding Bt cotton and choose the correct option.
• [(P)] Bt toxin is produced by Bacillus thuringiensis.
• [(Q)] The inactive protoxin gets activated in the acidic gut of insects.
• [(R)] Cry proteins create pores in the epithelial cells of insect midgut.
• [(S)] Different cry genes control different groups of insects.

• A. P, R and S are correct but Q is incorrect
• B. P and Q are correct but R and S are incorrect
• C. Only P and R are correct
• D. All statements are correct

Hint:

Bt toxin becomes active only in the alkaline gut of insects. The activated toxin forms pores in gut epithelium leading to insect death.

Answer 1

The Correct Option is A

Concept: Bt cotton is a genetically modified crop developed using genes obtained from the bacterium: \[ \textit{Bacillus thuringiensis} \] This bacterium produces insecticidal proteins called Cry proteins.

Step 1: Analyzing statement P. Bt toxin is naturally synthesized by: \[ \textit{Bacillus thuringiensis} \] Therefore statement P is correct.

Step 2: Analyzing statement Q. The toxin produced by the bacterium exists in inactive protoxin form. Activation occurs in:
• alkaline medium of insect gut and not in acidic medium. Hence statement Q is incorrect.

Step 3: Analyzing statement R. Activated toxin binds to epithelial cells of insect midgut and creates pores. This results in:
• cell swelling
• lysis
• death of insect larvae Therefore statement R is correct.

Step 4: Analyzing statement S. Different cry genes target different insects. Examples:
• cryIAb \(\rightarrow\) corn borer
• cryIAc \(\rightarrow\) cotton bollworm Hence statement S is correct. Final conclusion. Statements P, R and S are correct while Q is incorrect. Hence option (A) is correct. Final Answer: \[ \boxed{(A)} \]