Question

Plasmids are used in genetic engineering because they are

• A. Easily available
• B. Able to replicate
• C. Inert
• D. Able to integrate with host chromosome

Answer 1

The correct option is B Able to replicate

Genetic engineering
The modification of the genetic material (RNA or DNA) of organisms to use them to produce commercially important substances is called genetic engineering.

Basic process of genetic engineering
Basic process of genetic engineering is as follows:
● The gene of interest is removed from the cell of an organism and inserted into the vector DNA to form recombinant DNA.
● The formation of the rDNA is done using enzymes, endonucleases and ligases.
● The recombinant DNA is then transferred to the host cell where multiple copies of the DNA are made or the gene is expressed.

Vector
Vectors are the DNA molecules which can carry the foreign DNA fragment into the host cells for cloning.
Examples include plasmids.

Plasmid
Plasmids are extranuclear, circular, double stranded DNA. They are usually used as vectors in genetic engineering.

Features of plasmids as vector
Common features of plasmid as vector include the following:
● Presence of origin of replication (ori)
● Selectable markers
● Sites for the action of restriction endonucleases (restriction sites or cloning sites)
● Small sizes
● Copy number

Origin of replication
The ori site or origin of the replication site is a specific nucleotide sequence on the plasmid that initiates replication, without being dependent on genomic DNA for replication. Any piece of DNA when linked to this sequence can be made to replicate within the host cells. Plasmids are chosen as a vector for cloning in genetic engineering because of this reason.

Final answer
(B) Able to replicate