Central Dogma
The central dogma of molecular biology is an explanation of the
flow of genetic information within a biological system. It was first stated by
Francis Crick in 1956 and re-stated in a Nature paper published in 1970.
"The
central dogma of molecular biology deals with the detailed residue-by-residue
transfer of sequential information. It states that such information cannot be
transferred back from protein to either protein or nucleic acid. ”— Francis Crick
The central dogma has also been described
as "DNA makes RNA and RNA makes protein," a positive statement which
was originally termed the sequence hypothesis by Crick. However, this
simplification does not make it clear that the central dogma as stated by Crick
does not preclude the reverse flow of information from RNA to DNA, only ruling
out the flow from protein to RNA or DNA. Crick's use of the word dogma was
unconventional, and has been controversial.
The dogma is a framework for
understanding the transfer of sequence information between information-carrying
biopolymers, in the most common or general case, in living organisms. There are
3 major classes of such biopolymers: DNA and RNA (both nucleic acids), and
protein. There are 3×3 = 9 conceivable direct transfers of information that can
occur between these. The dogma classes these into 3 groups of 3: 3 general
transfers (believed to occur normally in most cells), 3 special transfers
(known to occur, but only under specific conditions in case of some viruses or
in a laboratory), and 3 unknown transfers (believed never to occur). The
general transfers describe the normal flow of biological information: DNA can
be copied to DNA (DNA replication), DNA information can be copied into mRNA
(transcription), and proteins can be synthesized using the information in mRNA
as a template (translation).
By:
Sohaib Hassan
7/22/2019