Question

Plasmid has been used as vector because

• A. It is circular DNA which have capacity to join to eukaryotic DNA.
• B. It can move between prokaryotic and eukaryotic cells.
• C. Both ends show replication.
• D. All of the above.

Answer 1

Answer: (D)

All of the above.

Plasmids are low molecular weight extrachromosomal DNA that carry origin of replication, restriction sites and selectable markers to confer readily selectable phenotypic traits on host cells. Plasmids require very few genes for their own replication and rest of it can be deleted and foreign sequences can be added to the plasmid.

Being circular molecule, it does not have difficulties associated with replication of chromosomal ends as is found in linear chromosomes due to requirement of a primer and template strand to the DNA polymerase enzyme. To move between different cells, plasmids have ori region that confers their replication in host and tra gene codes for transfer protein needed for transfer of plasmids from one cell to other.