Last update : August 9, 2013
The central dogma of molecular biology is not really a dogma, but a framework for understanding the transfer of sequenced information between biopolymers in living organisms. There are 3 major classes of such biopolymers :
In it’s simplest form, the dogma of molecular biology states that DNA makes RNA and RNA makes protein. The dogma was first stated by Francis Crick in 1958 and re-stated in a Nature paper (Vol 227) published in August 1970.
There are 3×3 = 9 conceivable direct transfers of information that can occur between these biopolymers classed into 3 groups :
- general transfers
- special transfers
- unknown transfers
The general transfers describe the normal flow of biological information :
- DNA Replication : process by which one double-stranded DNA molecule produces two identical copies of the molecule
- Transcription : process by which the information contained in a section of DNA is transferred to a newly assembled piece of messenger RNA (mRNA)
- Translation : process by which the messenger RNA (mRNA) produced by transcription is decoded by the sites of protein synthesis, the ribosomes, to produce a specific amino acid chain, or polypeptide, that will later fold into an active protein
Special transfers occur only under specific conditions in case of some viruses or in a laboratory. These transfers are RNA replication, reverse transcription and direct translation from DNA to protein.
Francis Crick believed that protein could not encode for DNA or RNA or other proteins and classed these processes in the unknown transfers. Prions, discovered in 1982 by Stanley B. Prusiner, are proteins that propagate themselves by making conformational changes in other molecules of the same type of protein. While this represents a transfer of information from protein to protein, prion interactions leave the sequence of the protein unchanged, and so are not technically considered an exception to the central dogma of molecular biology of Francis Crick.