(Molecular biology) In eukaryotes only - the processing of an immature mRNA molecule to create a mature mRNA, ready for translation into protein. Immediately following the transcription of a gene, the newly generated mRNA molecule contains regions of useful sequence known as exons interspersed with long regions of non-coding sequence known as introns. RNA splicing is the process by which the cell removes the intronic sequence, leaving only the functional exonic sequence. Some genes can be processed by RNA splicing in a number of ways (e.g. by leaving out certain exons or by including portions of normally intronic sequence), leading to the generation of alternative transcripts. This process allows a single gene to encode many different proteins.