which is not true for all cloning vectors ?

Options

A. These are independent of the control of chromosomal DNA
B. These get integrated into chromosomal DNA after transformation
C. They contain genes antibiotic resistance or some selectable marker
D. They have 'ori' region

Answer

To determine which statement is not true for all cloning vectors, we need to analyze each option based on the characteristics of cloning vectors.

### Step-by-Step Solution:

1. **Understanding Cloning Vectors**:
- Cloning vectors are DNA molecules used to carry foreign DNA into a host cell. They are essential tools in biotechnology for gene cloning.

2. **Characteristics of Cloning Vectors**:
- Cloning vectors should have:
- An **origin of replication (ori)**: This allows the vector to replicate independently within the host cell.
- **Selectable markers**: These are usually genes that confer antibiotic resistance or other traits that allow for the identification of successfully transformed cells.

3. **Analyzing the Statements**:
- **Statement A**: "These are independent of the control of chromosomal DNA."
- **Analysis**: While plasmids (a type of cloning vector) are independent and replicate on their own, some vectors like viral vectors integrate into the host's chromosomal DNA. Therefore, this statement is not true for all cloning vectors.

- **Statement B**: "These get integrated into chromosomal DNA after transformation."
- **Analysis**: This statement is true for certain vectors, particularly viral vectors, which integrate their DNA into the host genome. However, it does not apply to all cloning vectors, especially plasmids that remain independent.

- **Statement C**: "They contain genes for antibiotic resistance or some selectable marker."
- **Analysis**: This is a fundamental characteristic of cloning vectors, as selectable markers are crucial for identifying successful transformations. This statement is true for all cloning vectors.

- **Statement D**: "They have an ori region."
- **Analysis**: All cloning vectors must have an origin of replication (ori) to ensure they can replicate within the host. This statement is also true for all cloning vectors.

4. **Conclusion**:
- The statement that is not true for all cloning vectors is **Statement A**: "These are independent of the control of chromosomal DNA."

### Final Answer:
**Statement A** is not true for all cloning vectors.

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