Cloning Vector concepts genetic engineering

Plasmids are extrachromosomal, double standard, circular, self-replicating DNA molecules. Almost all the bacteria have plasmids containing a low copy number (1-4 per cell) or a high copy number (10-100 per cell). The size of plasmids varies from 1 to 500 kb.

Usually, plasmids contribute to about 0. 5 to 5. 0% of the total DNA of bacteria.

Example:Streptomyces sp. A plasmid is a naturally occurring extrachromosomal double stranded DNA, circular DNA. It replicates autonomously within bacterial cell.

Plasmid carries an origin of replication. Plasmid vectors are the simplest cloning vectors. It is most widely used for gene cloning.