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 tumour forming genes
B. Deleting tumor foming genes
C. Adding genes resistant to endonucleases
D. Deleting endonuclease

Answer

To solve the question regarding the modification of the tumor-inducing (Ti) plasmid into a non-pathogenic cloning vector, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Ti Plasmid**: The Ti plasmid is a naturally occurring plasmid found in the bacterium Agrobacterium tumefaciens, which is known for causing tumors in plants (crown gall disease). It contains genes that induce tumor formation.

2. **Modification Purpose**: The goal of modifying the Ti plasmid is to create a cloning vector that can deliver desired genes into plants without causing disease. This means we need to remove or alter the parts of the plasmid responsible for tumor formation.

3. **Analyzing the Options**:
- **Adding tumor forming genes**: This would make the plasmid pathogenic, which is contrary to the goal.
- **Deleting tumor forming genes**: This would remove the pathogenicity while retaining the ability to transfer genes into plant cells.
- **Adding genes resistant to endonuclease**: This does not directly relate to the pathogenicity or the delivery mechanism.
- **Deleting endonuclease**: This option does not address the tumor-inducing properties of the Ti plasmid.

4. **Conclusion**: The correct modification to make the Ti plasmid a non-pathogenic cloning vector while still being able to deliver genes of interest is to **delete the tumor-forming genes**.

### Final Answer:
The Ti plasmid has been modified by **deleting tumor-forming genes**.

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