From The School of Biomedical Sciences Wiki
When the transcription of eukaryotic DNA by RNA polymerase occurs, the DNA transcribed produces pre-mRNA which includes both introns and exons.
Introns are non-coding elements of DNA (however, often have a regulatory function). Exons are the protein coding regions of DNA.
Pre-mRNA is processed into mature mRNA by the removal and splicing of introns followed by the addition of a poly-A tail. The mature mRNA is then suitable for translation into the coded proteins.
Prokaryotic DNA only contain exons, whereas Eukaryotic DNA contain introns and exons.
The average length of a exon is 145 base pairs.
- ↑ 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.