Question

The toxin proteins isolated from {Bacillus thuringiensis, coded by which of the following genes would control cotton bollworms and corn borer, respectively ?}

• A. {cryIAc} and {cryIAb}
• B. {cryIIAb} and {cryIAc}
• C. {cryIAc} and {cryIIAb}
• D. {cryIAc} and {cryIIAb}

Hint:

Logic Tip: Pay close attention to the small letters! \textbf{A}c and II\textbf{A}b = Cotton. I\textbf{A}b = Corn. Don't let similar-looking gene names trick you during the exam.

Answer 1

The Correct Option is A

Concept:
Bacillus thuringiensis (Bt) produces insecticidal crystal (Cry) proteins during a particular phase of its growth. These toxins are highly insect-group specific. The genes coding for these proteins are called cry genes, and they are utilized in biotechnology to create pest-resistant genetically modified crops.
Step 1:
According to standard agricultural biotechnology, the toxic proteins encoded by the specific genes cryIAc and cryIIAb are highly effective at controlling the cotton bollworm pest.
Step 2:
A different specific gene is required to target the corn borer. The protein encoded by the gene cryIAb controls the corn borer.
Step 3:
The question asks for the genes that control the cotton bollworm first, followed by the corn borer second. We therefore need an option formatted as: (Cotton Bollworm Gene) and (Corn Borer Gene).
Step 4:
We need an option that pairs either cryIAc or cryIIAb with cryIAb. Option (1) pairs {cryIAc (which controls cotton bollworm) with cryIAb (which controls corn borer). Options (2), (3), and (4) merely pair the two cotton bollworm genes together, omitting the corn borer gene entirely.
Step 5:
Option (1) accurately represents the respective genes required for both pests.