Question

Bacterial plasmids often serve as cloning vectors. Describe the essential features of a plasmid vector. What are the advantages and applications of plasmids as cloning vectors?

Answer 1

A plasmid is a vector which is used for the transfer of genes from one organism to the other. It is inserted into the host bacterial cell and the bacterial cell is then transferred into the desirable organism.

Three main features that must be present in a plasmid vector are -

Presence of a site called as origin of replication. Because of this site, the plasmid will be able to undergo replication and maintain itself stability inside the host. It will not be lost.

Presence of a selectable marker gene like antibiotic resistance which will help in the selection of host cell which has taken up the plasmid and which has not taken up the plasmid.

Presence of a multiple cloning site or polylinker site which contains restriction site for many restriction enzymes. This must be present so that the plasmid can be cut and the foreign gene can be inserted at this site.

The applications and advantages of plasmids are a cloning vector are -

It can easily be isolated from a bacteria and can easily be manipulated to insert the gene of interest and then again can easily be inserted into the host bacterial cell.

It can easily be maintained inside the host cell and can replicate itself.

The selection process of transformants versus non transformants becomes easier when we use plasmid as a vector.

Plasmid can be used for the transfer of any gene of interest like gene encoding stress tolerance in bacteria, gene encoding any desirable protein or enzyme etc.

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