View source for Exon

When the transcription of&nbsp;[[Eukaryotic|eukaryotic]] [[DNA|DNA]] by&nbsp;[[RNA polymerase|RNA polymerase]]&nbsp;occurs,&nbsp;the [[DNA|DNA]] transcribed produces&nbsp;[[Pre-mRNA|pre-mRNA]] which includes both [[Introns|introns]] and exons. 

[[Introns|Introns]] are non-coding elements of DNA (however, often have a regulatory function). Exons are the [[Protein|protein]] coding regions of [[DNA|DNA]].&nbsp; 

Pre-mRNA is processed into mature [[MRNA|mRNA]]&nbsp;by the removal and splicing of&nbsp;[[Introns|introns]]&nbsp;followed by the addition of a&nbsp;[[Poly-A tail|poly-A tail]]. &nbsp;The mature [[MRNA|mRNA]] is then suitable for [[Translation|translation]]&nbsp;into the coded proteins.&nbsp; 

[[Prokaryotes|Prokaryotic]] [[DNA|DNA]] only contain exons, whereas&nbsp;[[Eukaryotic|Eukaryotic]] [[DNA|DNA]] contain&nbsp;[[Introns|introns]] and exons. 

The average length of a exon is 145 base pairs<ref>Alberts B., Johnson A., Lewis J., Raff M., Roberts K., Walter P. (2008) Molecular Biology of the Cell, 5th edition, New York: Garland Science. Page 207.</ref>.



=== References ===

<references />