USES OR APPLICATIONS OF PLASMID:

IN CLONING:

Plasmids are the most commonly used bacterial cloning vectors. These cloning vectors contain a site that allows DNA fragments to be inserted. After the gene of interest is inserted, the plasmids are introduced into bacteria by a process called transformation. These plasmids contain a selectable marker, usually an antibiotic resistance gene, which confer on the bacteria an ability to survive and proliferate in a selective growth medium containing the particular antibiotics. The cell after transformation are exposed to the selective media, and only cells containing the plasmid may survive. The vector may also contain other marker genes to facilitate selection of plasmid with cloned vector insert. Bacteria containing the plasmid can then be grown in large amounts, harvested and the plasmid of interest may then be isolated. A plasmid cloning vector is typically used to clone DNA fragments of up to 15 kbps. These cloning vectors can be plasmids, cosmids, bacterial artificial chromosome (BACs), yeast artificial chromosomes (YACs), or bacteriophages (phage-lambda and M13 phage) e.g., of two known cloning vectors are pBR322 and pUC19.

EXPRESSION:

Another major use of plasmids is to make large amount of proteins. Expression vector (plasmids) are used to introduce a specific gene into a target cell and commander cell's mechanisms produce a relevant gene product. It comprises of enhancers, promoter region, termination codon, transcription initiation sequences and translation initiation sequences in addition to features of a cloning vector. In this case, as the bacteria produces proteins to confer its antibiotics resistance, it can be induced to produce large amounts of proteins from the inserted gene. For e.g., insulin Example of expression vector is pET28a.

MUTAGENESIS:

It is a molecular biology method that is used to make specific and intentional changes to the DNA sequence of gene and any gene product. It is also called site specific mutagenesis or oligonucleotide directed mutagenesis. It is used for investigating the structure and biological activity of DNA, RNA and proteins.