Which of the following is incorrect?

Options

A. Both bacteriophages and plasmids can be used as cloning vectors
B. Bacteriophages have high copy numbers of their genome within bacterial cell
C. Cloning vectors must have an Ori
D. A good cloning vector definitely contains more than one recognition site for the restriction enzyme to be used

Answer

To determine which statement is incorrect regarding cloning vectors, let's analyze each statement step by step:

1. **Statement 1: Both bacteriophages and plasmids can be used as cloning vectors.**
- **Analysis**: Bacteriophages (viruses that infect bacteria) and plasmids (circular DNA molecules found in bacteria) are indeed both utilized as cloning vectors. They have high copy numbers, which is essential for cloning, and facilitate the selection of recombinant DNA.
- **Conclusion**: This statement is **true**.

2. **Statement 2: Bacteriophages have a high copy number of the genome within bacterial cells.**
- **Analysis**: Bacteriophages can replicate within bacterial cells, producing multiple copies (approximately 15 to 100) of their genome. This high copy number is a characteristic feature of bacteriophages.
- **Conclusion**: This statement is **true**.

3. **Statement 3: Cloning vectors must have an ORI (origin of replication).**
- **Analysis**: An origin of replication (ORI) is crucial for any cloning vector as it allows the replication of the inserted foreign DNA within the host cell. Without an ORI, the foreign DNA would not be replicated.
- **Conclusion**: This statement is **true**.

4. **Statement 4: A good cloning vector definitely contains more than one recognition site for the commonly used restriction enzymes.**
- **Analysis**: A good cloning vector should ideally have only one recognition site for each commonly used restriction enzyme. If there are multiple recognition sites for the same enzyme, it can lead to the vector being cut into multiple pieces, complicating the cloning process. Therefore, this statement is incorrect.
- **Conclusion**: This statement is **false**.

**Final Answer**: The incorrect statement is **Statement 4**.

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