Definition of plasmid in English:



  • A genetic structure in a cell that can replicate independently of the chromosomes, typically a small circular DNA strand in the cytoplasm of a bacterium or protozoan. Plasmids are much used in the laboratory manipulation of genes.

    Compare with episome
    • ‘For sporulation, diploid cells with plasmids were first grown in selective media.’
    • ‘The bacterium contains a plasmid, a circular piece of DNA that holds the gene and promoter sequence.’
    • ‘The replication control genes of bacterial plasmids face selection at two conflicting levels.’
    • ‘We note, however, that few if any of the genes borne by bacterial plasmids are under strong positive selection at all times.’
    • ‘Conjugative plasmids can mediate gene transfer between bacterial taxa in diverse environments.’


1950s: from plasma + -id.