Genetic element not contained within a chromosome. It occurs in many bacterial strains. Plasmids are circular DNA molecules that replicate independently of the bacterial chromosome. They are not essential for the bacterium but may give it a selective advantage. Some plasmids determine the production of proteins that can kill other bacteria; others make bacteria resistant to antibiotics. Plasmids are extremely valuable tools in the fields of molecular biology and genetics, specifically in the area of genetic engineering.
This entry comes from Encyclopædia Britannica Concise.
For the full entry on plasmid, visit Britannica.com.
Seen & Heard
What made you look up plasmid? Please tell us what you were reading, watching or discussing that led you here.