∞ generated and posted on 2016.12.15 ∞
Sequence found within reading frames that is edited out of RNA products.
|Introns are segments of RNA that are removed from newly transcribed RNAs in the process of what is known as RNA maturation.|
Especially in eukaryotes, within the reading frames of genes are found numerous intervening sequences or introns. During the RNA processing step of mRNA, these introns are catalytically removed, resulting in uninterrupted reading frames that then can be translated.
This process of intron removal is called RNA splicing and involves in part the action of complexes known as spliceosomes as well autocatalytic functions associated with the introns themselves.
Figure legend: Removal of introns from mRNA reading frame. The larger arrow heads indicate the direction that the mRNA will pass through the ribosome during translation, though that will occur only once the introns have been removed and the mRNA otherwise matured. Note that mRNA reading frames generally will begin with start codons, pass through numerous sense codons, and end with one or more stop codons.
The sequences that do not represent introns within the reading frames of these genes are described instead as exons. The interruption of exons by introns gives rise to the concept of split genes. For a given gene, introns often can be differentially removed, resulting in different combinations of exons and thus more than one gene product that may be produced per gene.
The word "intein" has been given to the protein equivalent of introns, i.e., oligopeptide segments that can be catalytically spliced out of proteins.