Question

Plasmids are used as cloning vectors because they

• A. Can be multiplied on culture
• B. Are self-replicating in bacterial cell
• C. Can be multiplied in lab with help of enzymes
• D. Replicate freely outside the cell

Hint:

To be an effective vector, a plasmid must have an 'ori', selectable markers (like antibiotic resistance genes), and unique cloning sites.

Answer 1

The Correct Option is B

Step 1: Plasmids are extra-chromosomal, circular, double-stranded DNA molecules found in bacteria.
Step 2: They possess an "Origin of Replication" (ori) sequence, which allows them to replicate independently of the bacterial chromosomal DNA.
Step 3: This self-replicating property makes them ideal for carrying and multiplying foreign DNA fragments (genes of interest) within a host cell.