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 enzymes and ligases
D. carrying an endotoxin gene from Bacillus thuringiensis

Answer

### Step-by-Step Solution

1. **Understanding the Question**: The question asks about the meaning of the prefix "Bt" in Bt cotton.

2. **Identifying Bt Cotton**: Bt cotton is a genetically modified organism (GMO) that has been engineered to be resistant to pests.

3. **Origin of the Name**: The "Bt" in Bt cotton stands for "Bacillus thuringiensis," which is a bacterium that produces a protein toxic to certain pests.

4. **Mechanism of Action**: The gene that encodes for the Bt toxin is inserted into the cotton plant's genome. This allows the cotton plant to produce the toxin itself, making it resistant to pests.

5. **Conclusion**: Therefore, the prefix "Bt" refers to the cotton that has been genetically modified to express the Bt toxin from Bacillus thuringiensis, which acts as a natural pesticide.

### Final Answer
The prefix "Bt" in Bt cotton means it carries an endotoxin gene from Bacillus thuringiensis, making it pest-resistant.

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