Read the following and answer questions from Q.1. to Q.5. given below:
Plants having foreign genes in their genome through genetic engineering are called transgenic plants. Genes can be incorporated either through a vector or through direct introduction of DNA. Bt cotton is a genetically modified organism which is pestresistant. It contains gene cry I Ac and cry II Ab of Bacillus thuringiensis. It is used to control lepidopterans, coleopterans and dipterans. Bt cotton can resist cotton bollworm and produce higher yields. Cry gene produces cry protein or Bt toxin. It is an endotoxin which remains as protoxin in plants and converted to active toxin after getting ingested by the insects. Alkaline pH of the insect gut solubilizes the protein crystals, the activated toxin creates pores to the mid guts wall of theinsects which cause them to death.
Cotton bollworms are killed by the protein encoded by the gene

Options

A. cry I Ac
B. cry I Ab
C. cry II Ab
D. both A and C

Explanation

### Step-by-Step Solution:

1. **Understanding Transgenic Plants**:
- Transgenic plants are those that have been genetically modified to contain foreign genes. This modification can be achieved through vectors or direct DNA introduction.

2. **Identifying Bt Cotton**:
- Bt cotton is a specific example of a transgenic plant that has been engineered to be resistant to pests. It contains genes from the bacterium *Bacillus thuringiensis*.

3. **Identifying the Genes**:
- The genes present in Bt cotton are Cry1Ac and Cry2Ab. These genes encode proteins that are toxic to certain insect pests.

4. **Mechanism of Action**:
- The Cry proteins produced by these genes act as endotoxins. They remain inactive (as protoxins) in the plant until ingested by the target insects.

5. **Effect on Cotton Bollworms**:
- The activated Cry proteins create pores in the midgut of the insects (like cotton bollworms), leading to their death. This mechanism is effective against various pests, including lepidopterans, coleopterans, and dipterans.

6. **Conclusion**:
- Since the question asks which genes are responsible for killing the cotton bollworm, we conclude that both Cry1Ac and Cry2Ab are involved in this process. Therefore, the correct answer is **both A (Cry1Ac) and C (Cry2Ab)**.

### Final Answer:
- The cotton bollworms are killed by the protein encoded by both Cry1Ac and Cry2Ab genes.

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