Question

What are cloning vectors? Briefly explain the characteristics of cloning vectors.

Hint:

Plasmids are the most common cloning vectors. Key features: Ori, selectable markers, multiple cloning sites, small size, and high copy number.

Answer 1

A cloning vector is a DNA molecule used to carry a foreign DNA fragment into a host organism where it can be replicated and expressed. Common cloning vectors include plasmids, bacteriophages, and cosmids.

Step 1: Examples. \[\begin{array}{rl} \bullet & \text{Plasmids: Small, circular DNA molecules in bacteria.} \\ \bullet & \text{Bacteriophages: Viruses that infect bacteria.} \\ \end{array}\]

Step 2: Characteristics of an Ideal Cloning Vector. \[\begin{array}{rl} 1. & \text{Origin of Replication (Ori): Allows autonomous replication within the host cell.} \\ 2. & \text{Selectable Marker: Gene for antibiotic resistance (e.g., ampicillin resistance) to identify transformed cells.} \\ 3. & \text{Cloning Sites (MCS – Multiple Cloning Site): A region with several unique restriction sites for insertion of foreign DNA.} \\ 4. & \text{Small Size: Easy to manipulate and transfer into host cells.} \\ 5. & \text{High Copy Number: Produces many copies of inserted DNA for large-scale cloning.} \\ \end{array}\]