ABSTRACT
The primary RNA transcript from a protein-coding gene in a eukaryotic cell must be modified by several RNA processing reactions in order to become a functional mRNA molecule. The 5' end is modified to form a 5 cap structure. Most pre-mRNAs are then cleaved near the 3' end and a poly(A) tail is added. Intron sequences are removed by RNA splicing. In eukaryotes, the product of transcription of a protein-coding gene is pre-mRNA which requires processing to generate functional mRNA. Certain pre-mRNAs contain more than one set of signal sequences for 3' end cleavage and polyadenylation. RNA editing is the name given to several reactions whereby the nucleotide sequence on an mRNA molecule may be changed by mechanisms other than RNA splicing. Individual nucleotides within the mRNA may be changed to other nucleotides, deleted entirely or additional nucleotides inserted.
