Which has the ability to transform normal cells into cancerous cell ?

Options

A. Ti plasmid
B. Retrovirus
C. All plasmids
D. Both (1) & (2)

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks which entities have the ability to transform normal cells into cancerous cells. This transformation is crucial in understanding how certain pathogens can induce tumor formation.

2. **Identifying Key Organisms**: Two key organisms are known for their ability to induce such transformations:
- **Agrobacterium tumefaciens**: This is a bacterium that infects plants and is known for its ability to transfer a specific piece of DNA called T-DNA (tumor DNA) into the plant cells. This T-DNA integrates into the plant genome and causes the plant cells to proliferate uncontrollably, leading to tumor formation.
- **Retroviruses**: These are a class of viruses that can infect animal cells. They can integrate their genetic material into the host cell's DNA, which can lead to uncontrolled cell division and cancer.

3. **Explaining the Mechanism**:
- **T-DNA from Agrobacterium**: The T-DNA carried by the Ti plasmid (tumor-inducing plasmid) of Agrobacterium tumefaciens is responsible for the transformation of normal plant cells into tumor cells. This is a well-studied mechanism in plant biotechnology.
- **Retroviral Mechanism**: Retroviruses, such as HIV, can insert their RNA into the host genome. This process can disrupt normal cellular functions and lead to cancerous transformations.

4. **Conclusion**: Both Agrobacterium tumefaciens (through its T-DNA) and retroviruses have the ability to transform normal cells into cancerous cells. Therefore, the answer to the question is that both of these entities can induce such transformations.

### Final Answer:
Both Agrobacterium tumefaciens (via T-DNA) and retroviruses have the ability to transform normal cells into cancerous cells.

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