The tumour -inducing ( Ti ) plasmid has now been modified into a cloning vector which is no more pathogenic to the plants but is still able to use the mechanisms to deliver genes of our interest into a variety of plants because Ti plasmid has been modified by

Options

A. Adding tumor-forming genes
B. Deleting tumor-forming genes
C. Adding genes resistant to endonucleases
D. Deleting endonuclease

Answer

To answer the question regarding how the tumor-inducing (Ti) plasmid has been modified into a cloning vector that is no longer pathogenic to plants, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Ti Plasmid**: The Ti plasmid is a naturally occurring plasmid found in certain species of Agrobacterium, particularly Agrobacterium tumefaciens. This plasmid is responsible for inducing tumors in plants by transferring part of its DNA into the plant cells.

2. **Pathogenic Nature**: The pathogenicity of the Ti plasmid is due to the presence of tumor-inducing genes. These genes cause uncontrolled growth in the plant cells, leading to the formation of tumors.

3. **Modification for Cloning**: To utilize the Ti plasmid as a cloning vector without causing harm to the plants, scientists have modified it. This modification involves removing the tumor-inducing genes from the plasmid.

4. **Result of Modification**: By deleting the tumor-forming genes, the modified Ti plasmid is no longer pathogenic. However, it retains the ability to transfer other genes of interest into plant cells, making it a useful tool for plant genetic engineering.

5. **Conclusion**: Therefore, the correct answer to the question is that the Ti plasmid has been modified by **deleting the tumor-forming genes**. This allows it to function as a cloning vector while being safe for the plants.

### Final Answer:
The Ti plasmid has been modified by deleting the tumor-forming genes, making it a non-pathogenic cloning vector that can still deliver genes of interest into plants.

---