A good cloning vect or should ha ve all except :-

Options

A. Origin of replication to start replication
B. Many recognition sites for single restriction enzyme
C. High copy number
D. Selectable marker

Answer

To answer the question about the characteristics of a good cloning vector, let's break down the essential features that a cloning vector should have, and identify which one is not necessary.

### Step-by-Step Solution:

1. **Definition of a Cloning Vector**: A cloning vector is a DNA molecule used to transport foreign genetic material into a host cell. It is essential for cloning and expressing genes.

2. **Origin of Replication**: A good cloning vector must have an origin of replication (ori) to ensure that it can replicate within the host cell.

3. **Multiple Cloning Sites (MCS)**: It should contain multiple cloning sites, which are regions that have several restriction enzyme recognition sites. This allows for the insertion of foreign DNA at various locations.

4. **Selectable Marker**: A cloning vector should have a selectable marker (like antibiotic resistance genes) that allows for the identification of cells that have successfully taken up the vector.

5. **High Copy Number**: A good cloning vector should be capable of producing many copies of itself within the host cell. This is referred to as having a high copy number.

6. **Size of the Vector**: The vector should be small enough to be easily manipulated but large enough to carry the foreign DNA. However, the size is not a strict requirement as long as it can accommodate the DNA of interest.

7. **Recognition Sites for Restriction Enzymes**: A good cloning vector should have recognition sites for restriction enzymes, but having many recognition sites for a single restriction enzyme is not necessary. It is more beneficial to have multiple sites for different enzymes.

8. **Conclusion**: Based on the above points, a good cloning vector should have all the features mentioned, except for "many recognition sites for a single restriction enzyme." This feature is not essential and could even be counterproductive.

### Final Answer:
A good cloning vector should have all except **many recognition sites for a single restriction enzyme**.

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