Question

Assertion (A): Genetically modified microbes help in crop protection.
Reason (R): Bacillus thuringiensis (Bt) bacteria control insects by producing prototoxins.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

To test the explanation link, read them together using "because": "Genetically modified microbes protect crops because Bt bacteria naturally produce a protoxin." This link lacks direct continuity, confirming Option (B).

Answer 1

The Correct Option is B

Concept: This question format requires evaluating the truth values of the Assertion and Reason statements individually, and then determining if a valid cause-and-effect relationship exists between them.
• Microbes can be genetically modified to carry specific genes that protect crop plants against pests and pathogens.
• Bacillus thuringiensis naturally synthesizes crystalline insecticidal proteins called protoxins. These inactive protoxins convert into active toxins in the alkaline gut environment of susceptible insects.

Step 1: Analyze the Assertion statement.
Genetically modified microbes (such as bacteria engineered with specific biocontrol vectors) or the direct introduction of microbial genes into crops play a significant role in modern crop protection strategies. Hence, Assertion (A) is a true statement.

Step 2: Analyze the Reason statement.
Bacillus thuringiensis bacteria produce an inactive crystal protein known as a protoxin. When ingested by an insect, the alkaline pH of the insect's midgut solubilizes the crystals, converting the protoxin into its active form. This active toxin binds to epithelial cells, creating pores that lead to cell lysis and death of the pest. Thus, Reason (R) is also a true statement.

Step 3: Determine if the Reason explains the Assertion.
While both statements are factually correct, the Reason describes the natural mechanism of the wild-type bacterium Bacillus thuringiensis producing a protoxin. It does not explain how genetically modified microbes help in crop protection. Thus, Reason (R) is not the correct explanation for Assertion (A). This corresponds to Option (B).