Question

Bacillus thuringiensis CryA controls certain caterpillar pests by

• A. turning toxic in the acidic pH of their gut medium
• B. turning toxic in the alkaline medium of their gut
• C. repelling them from the crops
• D. inducing satiation in them

Hint:

Remember: Bt Cry proteins become toxic only in the alkaline gut environment of pests, which is why they are safe for humans with acidic stomach conditions.

Answer 1

The Correct Option is B

Step 1: Understanding Bt CryA protein.
Bacillus thuringiensis (Bt) produces Cry proteins, which are used in genetically modified crops to provide pest resistance. 
Step 2: Activation of CryA protein. 
When caterpillar pests ingest CryA protein, it reaches their gut, where the alkaline pH environment activates the CryA protein. This activated toxin binds to the gut epithelial cells of the insect, leading to cell lysis and ultimately killing the pest. 
Step 3: Eliminate other options.
Option (1): CryA is not activated in acidic pH.
Option (3): CryA doesn't repel insects; it kills them.
Option (4): It does not induce satiation.
Thus, the correct answer is that CryA becomes toxic in the alkaline medium of the caterpillar gut.