Plasmid

A plasmid is an independent, circular, self-replicating DNA molecule that carries only a few genes. [1] Plasmids can be absorbed by cells, and the independent DNA inserted into the cell's genes, and thusly expressed. Plasmids often contain genes for antibiotic resistance and are used often in biological transformation experiments as a check to see if the implanted genes worked (if the cell is resistant to a particular anti-biotic that has a resistance gene on the plasmid with the gene of interest the cells will live in the environment with the anti-biotic; eliminating any cells that did not accept the plasmid).