GATE BT 2019 • Q11
MCQ • 1 Mark
Section 3: Genetics, Cellular and Molecular Biology
Recombinant DNA technology
Subtopic: Fundamentals of Recombinant DNA technology
Question Statement:
The Bt toxin gene from Bacillus thuringiensis used to generate genetically modified crops
Options:
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(A) cry
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(B) cro
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(C) cdc
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(D) cre
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2019 Q.11)**
**1. Governing Concept**:
- **Topic**: Plant Biotechnology & Transgenic Pest Resistance (Bt Crops)
- The soil bacterium *Bacillus thuringiensis* produces parasporal crystalline protein endotoxins (protoxins) during sporulation.
- These insecticidal crystal proteins are encoded by **cry genes** (e.g., *cry1Ac*, *cry1Ab*, *cry2Ab*), which are engineered into transgenic crops (Bt cotton, Bt corn, Bt brinjal) to confer resistance against lepidopteran, coleopteran, and dipteran insect pests.
**2. Option Analysis**:
- **Option (A) [cry] is CORRECT**: The specific gene encoding Bt delta-endotoxin crystal proteins.
- **Option (B) [cro] is INCORRECT**: Encodes the Cro repressor in bacteriophage lambda lytic/lysogenic switch.
- **Option (C) [cdc] is INCORRECT**: Cell division cycle genes (e.g., *cdc2/CDK1*).
- **Option (D) [cre] is INCORRECT**: Site-specific recombinase enzyme in Cre-loxP recombination.
**3. Final Answer**:
- **Correct Choice**: **A**
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