Editing Messenger RNA (section)

=== Monocistronic versus polycistronic mRNA ===
{{see also|Cistron}}
An mRNA molecule is said to be monocistronic when it contains the genetic information to [[Translation (genetics)|translate]] only a single [[protein]] chain (polypeptide). This is the case for most of the [[Eukaryote|eukaryotic]] mRNAs.<ref name="Kozak_1983">
{{cite journal | vauthors = Kozak M | title = Comparison of initiation of protein synthesis in procaryotes, eucaryotes, and organelles | journal = Microbiological Reviews | volume = 47 | issue = 1 | pages = 1–45 | date = March 1983 | pmid = 6343825 | pmc = 281560 | doi = 10.1128/MMBR.47.1.1-45.1983}}
</ref><ref>{{cite journal | vauthors = Niehrs C, Pollet N | title = Synexpression groups in eukaryotes | journal = Nature | volume = 402 | issue = 6761 | pages = 483–487 | date = December 1999 | pmid = 10591207 | doi = 10.1038/990025 | bibcode = 1999Natur.402..483N | s2cid = 4349134 }}</ref> On the other hand, polycistronic mRNA carries several [[open reading frame]]s (ORFs), each of which is translated into a polypeptide. These polypeptides usually have a related function (they often are the subunits composing a final complex protein) and their coding sequence is grouped and regulated together in a regulatory region, containing a [[Promoter (biology)|promoter]] and an [[Operator (biology)|operator]]. Most of the mRNA found in [[bacteria]] and [[archaea]] is polycistronic,<ref name="Kozak_1983"/> as is the human mitochondrial genome.<ref name="MercerNeph2011">{{cite journal | vauthors = Mercer TR, Neph S, Dinger ME, Crawford J, Smith MA, Shearwood AM, Haugen E, Bracken CP, Rackham O, Stamatoyannopoulos JA, Filipovska A, Mattick JS |author-link10=John Stamatoyannopoulos | title = The human mitochondrial transcriptome | journal = Cell | volume = 146 | issue = 4 | pages = 645–658 | date = August 2011 | pmid = 21854988 | pmc = 3160626 | doi = 10.1016/j.cell.2011.06.051 }}</ref> Dicistronic or bicistronic mRNA encodes only two [[protein]]s.