Editing Primary transcript (section)

===Polyadenylation===
{{Main|Polyadenylation}}
In eukaryotes, polyadenylation further modifies pre-mRNAs during which a structure called the [[poly-A tail]] is added.<ref name="Cooper GM"/> Signals for polyadenylation, which include several RNA sequence elements, are detected by a group of proteins which signal the addition of the poly-A tail (approximately 200 nucleotides in length). The polyadenylation reaction provides a signal for the end of transcription and this reaction ends approximately a few hundred nucleotides downstream from the poly-A tail location.<ref name="Cooper GM"/>