Question

Some strains of Bacillus thuringiensis produce proteins that kill insects. Which one of the following is not killed by proteins of Bacillus thuringiensis?

• A. Cotton bollworm
• B. Tapeworm
• C. Tobacco budworm
• D. Armyworm

Hint:

Bt toxins are effective against insects like bollworms and armyworms but not against parasitic worms like tapeworms.

Answer 1

The Correct Option is B

• Definition of Bt Proteins: Bacillus thuringiensis (Bt) produces crystal proteins (Cry toxins) that target the digestive systems of specific insects, particularly lepidopterans, coleopterans, and dipterans.
• Option Analysis:
  • (1) Cotton bollworm: A lepidopteran pest, susceptible to Bt toxins. This is incorrect (killed).
  • (2) Tapeworm: A parasitic flatworm (platyhelminth) that lives in the intestines of vertebrates, not targeted by Bt proteins which are specific to insects. This is correct (not killed).
  • (3) Tobacco budworm: Another lepidopteran pest, killed by Bt toxins. This is incorrect (killed).
  • (4) Armyworm: A lepidopteran larva, also susceptible to Bt. This is incorrect (killed).
• Mechanism Insight: Bt toxins bind to receptors in the midgut of susceptible insects, causing paralysis and death, but have no effect on non-insect parasites like tapeworms.
• Conclusion: The correct answer is (2) Tapeworm, as it is not an insect and thus not affected by Bt proteins.