What do plasmids have to do with transformation?
Plasmids are circular rings of DNA that exists naturally in bacteria, providing the bacterium with temporary advantages such as antibiotic resistance or the ability to digest certain compounds. Biologists have utilized plasmids as a vehicle to inject genes of interest into cells or bacteria, by cutting the plasmid open with restriction enzymes and then inserting the gene by ligation. The plasmid containing the gene is then transferred into the bacterium in the process of transformation. Currently, “designer” plasmids are available commercially, which usually contain three components: a strong promoter (such as lac) to increase protein yield, or an inducible promoter which functions like a switch where you could turn the target gene “on” or “off”, antibiotic resistance genes for clonal selection, and a plethora of restriction sites to facilitate DNA incorperation.
