What is a vector in biotechnology? How does a plasmid vector work?

What is a vector in biotechnology? How does a plasmid vector work?


A vector is a DNA molecule used as a vehicle to artificially carry foreign genetic material into another cell, where it can be replicated or expressed. A vector containing foreign DNA is termed recombinant DNA.


1) As the cloning vector can be stably maintained in an organism, the vector contains features that allow for the convenient insertion or removal of DNA.

– After being cloned into a cloning vector, the DNA fragment can be further sub-cloned into another vector that can be used with even more specificity.

2) Gene transfer into plant cells is commonly performed using the soil bacterium Agrobacterium tumefaciens, which acts as a vector and inserts a large plasmid into the host cell.

3) Vectors carry antibiotic resistant genes and spread them in the whole human or animal body. In this way many diseases of humans and animals can be treated.

Antibiotic resistance genes carried by vectors can be used to test for expression of the plasmid DNA, on antibiotic petri plates.

4) Vectors carry those genes which are involved in metabolic activities and are helpful in digesting the pollutants from the environment.

5) They are also capable of producing antibacterial proteins

6) Vectors also able to carry the genes which are concerned with increasing the pathogenicity of bacteria which cause diseases like anthrax and tetanus.

7) Plasmids are used to make large amounts of proteins. Bacterium can be induced to produce large amounts of proteins from the inserted gene. This is a cheap and easy way of mass-producing a gene or the protein it then codes for; for example, insulin or even antibiotics.

It is possible for plasmids of different types to coexist in a single cell. Several different plasmids have been found in E. coli. However, related plasmids are often incompatible, in the sense that only one of them survives in the cell line, due to the regulation of vital plasmid functions….


Bacteria contain plasmids – small circular DNA molecules.

Every plasmid has its own ‘origin of replication’ – a stretch of DNA that ensures it gets replicated (copied) by the host bacterium.

For this reason, plasmids can copy themselves independently of the bacterial chromosome, so there can be many copies of a plasmid – even hundreds – within one bacterial cell.

Plasmids contain genes, For instance, many plasmids contain genes that, when expressed, make the host bacterium resistant to an antibiotic Other plasmids contain genes that help the host to digest unusual substances or to kill other types of bacteria.

Under stressful conditions, bacteria with the plasmid will live longer – and have more opportunity to pass on the plasmid to daughter cells or to other bacteria. Bacteria without the plasmid are less likely to survive and reproduce.


A Typical plasmid vector has:

– origin of replication (to ensure the vector is copied within bacteria)

– a gene for antibiotic resistance (to ensure the vector is not lost by bacteria)

– set of recognition sites for restriction enzymes (to make it straightforward to insert foreign DNA into the vector).

Plasmids have been key to the development of molecular biotechnology. They act as delivery vehicles, or vectors, to introduce foreign DNA into bacteria. Using plasmids for DNA delivery began in the 1970s when DNA from other organisms was first ‘cut and pasted’ into specific sites within the plasmid DNA. The modified plasmids were then reintroduced into bacteria.

Plasmids may be :

– conjugative/transmissible

– non-conjugative.

Conjugative plasmids mediate DNA transfer through conjugation and therefore spread rapidly among the bacterial cells of a population.

Nonconjugative plasmids do not mediate DNA through conjugation….

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