Plasmid

A plasmid is a small, <a href="/facts/Extrachromosomal_DNA/SKgfpl5s">extrachromosomal DNA</a> molecule within a cell that is physically separated from <a href="/facts/GDNA/UeLsDBlw">chromosomal DNA</a> and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in <a href="/facts/Bacteria/wC8xSCsU">bacteria</a> and <a href="/facts/Archaea/Adxh0aHw">archaea</a>; however plasmids are sometimes present in and <a href="/facts/Eukaryote/SkwyPLMA">eukaryotic organisms</a> as well. Plasmids often carry useful genes, such as those involved in <a href="/facts/Antibiotic_resistance/jsbAywgx">antibiotic resistance</a>, <a href="/facts/Virulence/TYmX1Fa6">virulence</a>, <a href="/facts/Secondary_metabolism/F46tbTNA">secondary metabolism</a> and <a href="/facts/Bioremediation/zft68Ez9">bioremediation</a>. While chromosomes are large and contain all the essential genetic information for living under normal conditions, plasmids are usually very small and contain additional genes for special circumstances.
<a href="/facts/Artificial_plasmids/Ww5pxHRc">Artificial plasmids</a> are widely used as <a href="/facts/Vector_(molecular_biology)/XMp9Qaap">vectors</a> in <a href="/facts/Molecular_cloning/Te56373e">molecular cloning</a>, serving to drive the replication of <a href="/facts/Recombinant_DNA/dT3PL7M6">recombinant DNA</a> sequences within host organisms. In the laboratory, plasmids may be introduced into a cell via <a href="/facts/Transformation_(genetics)/n82cCRCu">transformation</a>. Synthetic plasmids are available for procurement over the internet by various vendors using submitted sequences typically designed with software, if a design does not work the vendor may make additional edits from the submission.
Plasmids are considered <a href="/facts/Replicon_(genetics)/a9FtIa42">replicons</a>, units of DNA capable of replicating autonomously within a suitable host. However, plasmids, like <a href="/facts/Virus/mf88Bcbl">viruses</a>, are not generally classified as <a href="/facts/Life/DNw7NUId">life</a>. Plasmids are transmitted from one bacterium to another (even of another species) mostly through <a href="/facts/Bacterial_conjugation/WfeyKYC4">conjugation</a>. This host-to-host transfer of genetic material is one mechanism of <a href="/facts/Horizontal_gene_transfer/FPyUIsf2">horizontal gene transfer</a>, and plasmids are considered part of the <a href="/facts/Mobilome/tMaTYvQV">mobilome</a>. Unlike viruses, which encase their genetic material in a protective protein coat called a <a href="/facts/Capsid/hm7V6Ewm">capsid</a>, plasmids are "naked" DNA and do not encode genes necessary to encase the genetic material for transfer to a new host; however, some classes of plasmids encode the <a href="/facts/Pilus/xCNEXUdy">conjugative "sex" pilus</a> necessary for their own transfer. Plasmids vary in size from 1 to over 400 k<a href="/facts/Base_pair/xmPpPQ9W">bp</a>, and the number of identical plasmids in a single <a href="/facts/Cell_(biology)/bLM9UQvy">cell</a> can range from one up to thousands.

Plasmid open-in-new

Plasmid