Definition of Plasmid

A plasmid is a small, circular, extrachromosomal DNA molecule which is double-stranded. It is present in all the prokaryotic cells and in some eukaryotic cells as well. The genes present in these plasmids provide the bacterial cells with extra genetic advantages such as resistance to antibiotics. A plasmid consists of about more than one thousand base pairs.


During binary fission, when the cell divides, every daughter cell receives a copy of this plasmid. These plasmids can also be transferred from one bacterial cell to the other by the process of conjugation. The plasmids are being employed as a tool to clone, transfer and manipulate a number of genes.


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