B. thuringiensis forms protein crystals during a particular phase of their growth. The toxin is coded by a gene named cry. There are a number of them. Which is not an example of such plants ?

Options

A. cryIAc
B. Cry II Ab
C. sry
D. cryIAb

Answer

To answer the question about which plant is not an example of those modified with the Bacillus thuringiensis (Bt) cry genes, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Bacillus thuringiensis (Bt)**:
- Bt is a bacterium that produces protein crystals containing toxins that are harmful to certain insects. These toxins are encoded by genes known as cry genes.

2. **Identify the Function of Cry Genes**:
- The cry genes produce proteins that, when ingested by insects, become activated in the alkaline environment of the insect gut. This leads to the formation of pores in the gut cells, causing swelling and ultimately the death of the insect.

3. **Recognize Common Bt Crops**:
- Crops that have been genetically modified to express Bt toxins include cotton (to combat cotton bollworm) and corn (to combat corn borer). These crops are examples of plants that have been engineered to include cry genes.

4. **Examine the Options Provided**:
- The question likely provides a list of plants, among which some are genetically modified with Bt cry genes and one is not. We need to identify the one that does not belong to this category.

5. **Select the Correct Answer**:
- Based on the common examples of Bt crops (like cotton and corn), we can determine which option does not represent a plant that has been modified with Bt cry genes.

### Conclusion:
The plant that is not an example of those modified with Bacillus thuringiensis cry genes is the one that does not have any association with the mentioned insect pests or is not genetically engineered with the cry genes.