Name any two natural cloning vectors. Give reasons that make them act as cloning vectors. Write the two characteristics the engineered vectors are made to possess

Correct Answer:
Natural cloning vectors: Plasmids and bacteriophages.
Reasons: Ability to replicate within bacterial cells and a high copy number within the bacterial cells.
Characteristics of engineered vectors: Easy linking of foreign DNA, and selection of recombinants from non-recombinants (selectable marker).

Step-by-Step Explanation:

1. Natural Cloning Vectors:
Cloning vectors are DNA molecules used as vehicles to artificially carry foreign genetic material into another cell, where it can be replicated and/or expressed. Two major natural cloning vectors are:
• Plasmids: Autonomously replicating, extra-chromosomal, circular double-stranded DNA molecules found naturally in many bacteria.
• Bacteriophages: Viruses that infect bacteria by injecting their genetic material, which then replicates inside the bacterial cell.

2. Reasons That Make Them Act as Cloning Vectors:
Plasmids and bacteriophages are uniquely suited to be vectors due to two key properties:
• Ability to Replicate Within Bacterial Cells: They possess an "origin of replication" (ori) sequence, allowing them to replicate independently of the host bacterial chromosome.
• High Copy Number: They can maintain a high number of copies within a single bacterial cell. A high copy number ensures that the cloned gene linked to the vector is amplified in large quantities.

3. Characteristics of Engineered Vectors:
Natural vectors are often modified or "engineered" to make gene cloning simpler and more efficient. Two essential characteristics engineered into modern vectors are:
• Easy Linking of Foreign DNA: Engineered vectors contain unique restriction sites (cloning sites) where specific restriction enzymes can make cuts, allowing foreign DNA to be easily inserted.
• Selection of Recombinants (Selectable Marker): They contain marker genes (such as resistance to antibiotics like ampicillin or tetracycline) that allow researchers to easily differentiate and select recombinant host cells from non-recombinants.