In many cases, the splicing process creates a range of unique proteins by varying the exon composition of the same messenger RNA. This phenomenon is called alternative splicing. Alternative splicing can occur in many ways. Exons can be extended or skipped, or introns can be retained.
Eukaryotes vs prokaryotes
Splicing occurs in all the kingdoms or domains of life, however, the extent and types of splicing can be very different between the major divisions. Eukaryotes splice many protein-coding messenger RNAs and some non-coding RNAs. Prokaryotes, on the other hand, splice rarely. Another important difference is that prokaryotes completely lack spliceosomes.
The coding regions of the gene are separated by non-coding DNA which is not involved in protein expression. The non-coding regions, the introns, are cut from the precursor mRNAs in a process Sharp called "splicing". The split gene structure was found to be common to most eukaryotic genes.
- Some introns are self-splicing.
- Berget S.M; Moore C. and Sharp P.A. (1977). "Spliced segments at 5' terminus of adenovirus 2 late messenger-RNA". Proc. Natl. Acad. Sci. USA 74 (8): 3171–5. doi:10.1073/pnas.74.8.3171. PMC 431482. PMID 269380.
- Chow L.T. et al (1977). "A map of cytoplasmic RNA transcripts from lytic adenovirus type 2, determined by electron microscopy of RNA:DNA hybrids". Cell 11 (4): 819–836. doi:10.1016/0092-8674(77)90294-X. PMID 890740.