Cultivation of Bt. Cotton has been much in the news. The prefix Bt. Means :

Options

A. " Barium treated" cotton seeds
B. "Bigger thread " variety cotton with better tensile strength
C. Produced by " biotechnology " using restriction enzymes and ligases
D. Carrying an endotoxin gene from Bacillus thuringiensls

Answer

**Step-by-Step Solution:**

1. **Understanding the Prefix "Bt":** The prefix "Bt" in Bt cotton refers to a specific bacterium known as Bacillus thuringiensis.

2. **Identifying Bacillus thuringiensis:** Bacillus thuringiensis is a soil-dwelling bacterium that produces a protein known as an endotoxin.

3. **Function of the Endotoxin:** The endotoxin produced by Bacillus thuringiensis is called Bt toxin. This toxin is effective against certain insect pests.

4. **Cloning and Expression:** The gene responsible for producing the Bt toxin has been cloned and inserted into cotton plants, allowing them to express this toxin.

5. **Purpose of Bt Cotton:** The primary purpose of Bt cotton is to provide resistance to insects, reducing the need for chemical insecticides.

6. **Conclusion:** Therefore, the prefix "Bt" in Bt cotton stands for Bacillus thuringiensis, which is associated with the production of an endotoxin that helps in pest resistance.

**Final Answer:** The prefix "Bt" means Bacillus thuringiensis.

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