Editing Primary transcript (section)

===5' capping===
{{Main|Five-prime cap}}
Shortly after transcription is initiated in eukaryotes, a pre-mRNA's 5' end is modified by the addition of a [[5' cap|7-methylguanosine cap]], also known as a 5' cap.<ref name="Cooper GM"/> The 5' capping modification is initiated by the addition of a [[Guanosine triphosphate|GTP]] to the 5' terminal nucleotide of the pre-mRNA in reverse orientation followed by the addition of methyl groups to the G residue.<ref name="Cooper GM"/> 5' capping is essential for the production of functional mRNAs since the 5' cap is responsible for aligning the mRNA with the ribosome during translation.<ref name="Cooper GM"/>