What is true about Bt toxin?

Options

A. The inactive protoxin gets converted into active form in the insect gut
B. Bt protein exists as active toxin in the Bacillus
C. The activated toxin enters the ovaries of the pest to sterilise it and thus, prevent its multiplication.
D. The concerned Bacillus has antitoxins

Answer

**Step-by-Step Solution:**

1. **Definition of Bt Toxin**: Understand that Bt toxin is produced by the bacterium Bacillus thuringiensis, which is a gram-positive bacterium. This bacterium is known for its ability to produce a toxin that is effective against certain pests.

2. **Biological Pesticide**: Recognize that Bt toxin is used as a biological pesticide. This means it is utilized in agriculture to control pest populations without the use of synthetic chemicals.

3. **Cry Gene**: Identify that the gene responsible for producing Bt toxin is known as the cry gene. This gene is crucial for the synthesis of the Bt protein.

4. **Protoxin Formation**: Note that the Bt protein exists as a protoxin, which is an inactive form of the toxin. This protoxin is present in the gut of the Bacillus thuringiensis.

5. **Activation in Insect Gut**: Understand that when the protoxin is ingested by an insect, the pH of the insect's gut activates the protoxin, converting it into its active form.

6. **Mechanism of Action**: The activated Bt toxin then disrupts the gut of the insect, leading to the death of the pest. This is the mechanism through which Bt toxin acts as an effective pesticide.

7. **Evaluating Statements**:
- **Statement A**: The inactive protoxin gets converted into the active form in the insect gut. (True)
- **Statement B**: Bt protein exists as an active form in the bacillus. (False - it exists as a protoxin)
- **Statement C**: The activated toxin enters the ovary of the pest. (False - it remains in the gut)
- **Statement D**: The concerned bacillus has antitoxin. (False - it does not possess antitoxin)

8. **Conclusion**: Based on the evaluation of the statements, the correct answer is that the inactive protoxin gets converted into the active form in the insect gut.

**Final Answer**: The correct statement about Bt toxin is that the inactive protoxin gets converted into the active form in the insect gut.

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