Messenger RNA

(mRNA); the RNA reflecting the exact nucleotide sequence of the genetically active DNA and carrying the "message" of the latter, coded in its sequence, to the cytoplasmic areas where protein is made in amino acid sequences specified by the mRNA

Description
Following transcription in the nucleus as pre-mRNA, the RNA molecule is processed in the nucleus to remove intervening, non-coding sequences (introns) by splicing and (usually) to add a poly(A) tail at the 3' end of the molecule prior to export to the cytosol through nuclear pores. Intracellular signalling influences the processing of mRNA, leading, e.g., to alternative splicing and in final consequence the production of differently-sized proteins from one and the same DNA sequence. The mature mRNA still contains non-coding regions (the 5'- and 3'-untranslated regions), that control the binding of transcription and other factors, besides the open reading frame (ORF) of the protein(s) it encodes. Many viruses have RNA genomes, which are often optimised to function as multi-cistronic mRNA, i.e. as mRNAs that encode several proteins, often with partially overlapping ORFs. Syn informational RNA, template RNA