Cultivation of Bt cotton has been much in the news. The prefix ''Bt'' means

Options

A. 'Barium-treated'' cotton seeds
B. 'Bigger thread '' variety of cotton with better tensile strength
C. Produced by ''biotechnology'' using restriction enzyme and ligase
D. Carrying an endotoxin gene from Bacillis thuringiensis.

Answer

To solve the question regarding the prefix "Bt" in Bt cotton, we will follow these steps:

### Step-by-Step Solution:

1. **Understanding Bt Cotton**:
- Bt cotton is a genetically modified organism (GMO) specifically designed to be resistant to certain pests, particularly the cotton bollworm. This resistance is achieved through genetic engineering.

2. **Analyzing the Options**:
- **Option A**: Barium treated cotton seeds - This option is incorrect as barium treatment has no relevance to the genetic modification of cotton.
- **Option B**: Bigger thread variety of cotton with better tensile strength - This option is also incorrect because Bt cotton is not primarily about enhancing the physical properties of the cotton fibers.
- **Option C**: Produced by biotechnology using restriction enzyme and ligand - While Bt cotton is produced using biotechnology, this option does not accurately describe what "Bt" stands for.
- **Option D**: Carrying an endotoxin gene from Bacillus thuringiensis - This option is correct. Bt cotton contains a gene from the bacterium Bacillus thuringiensis, which produces a protein that is toxic to certain insects.

3. **Conclusion**:
- The prefix "Bt" in Bt cotton stands for "Bacillus thuringiensis," indicating that the cotton has been genetically modified to express a gene from this bacterium, which provides resistance to insect pests.

### Final Answer:
The prefix "Bt" means carrying an endotoxin gene from Bacillus thuringiensis.

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