plasmid

What it means

1. biologyA loop of double-stranded DNA that is separate from — and replicates independently of — the chromosomes; such loops are most commonly found in bacteria, but they are also sometimes found in archaeans and eukaryotic cells, and they are used in genetic engineering as a vector for gene transfer.

   Bacteria are happy to absorb little rings of DNA called plasmids and adopt them as their own.

   1999, Matt Ridley, Genome, Harper Perennial, published 2004, page 247

   3 more examples

   These discussions have left a plethora of terms adrift: pangenes, bioblasts, plasmagenes, plastogenes, chondriogenes, cytogenes and proviruses, which have lost their original utility owing to the accretion of vague or contradictory connotations. At the risk of adding to this list, I propose plasmid as a generic term for any extrachromosomal hereditary determinant.

   1952 October 28, J. Lederberg, “Cell genetics and hereditary symbiosis”, in Physiological Reviews, volume 32, number 4, page 403

   This is how the F (for "fertility") plasmid, which forms the basis of a lot of classical E. coli genetics, is transferred from one cell to another.

   1995, Christopher Howe, Gene Cloning and Manipulation, page 144

   Plasmids have an essential impact on productivity. Related factors are plasmid copy number, structural plasmid stability and segregational plasmid stability.

   2004, Karl Friehs, “Plasmid Copy Number and Plasmid Stability”, in M. Beyer, T. Scheper, editors, New Trends and Developments in Biochemical Engineering, volume 86, page 47

In a sentence

These discussions have left a plethora of terms adrift: pangenes, bioblasts, plasmagenes, plastogenes, chondriogenes, cytogenes and proviruses, which have lost their original utility owing to the accretion of vague or contradictory connotations. At the risk of adding to this list, I propose plasmid as a generic term for any extrachromosomal hereditary determinant.

1952 October 28, J. Lederberg, “Cell genetics and hereditary symbiosis”, in Physiological Reviews, volume 32, number 4, page 403

Where it comes from

From plasma + -id, coined by American molecular biologist Joshua Lederberg in 1952.