Central dogma of molecular biology
The central dogma of molecular biology is a 1958 published by Francis Crick hypothesis about the possible flow of information between the biopolymers DNA, RNA and protein. Describes the transmission of the information by the order ( sequence) of monomers (nucleotides in DNA and RNA, amino acids in proteins ) is fixed.
In Crick's original form, the hypothesis states:
In 1970, Crick, an alternative formulation of the dogma to:
The Central Dogma - even if there are critical voices - widely accepted and is still regarded as one of the cornerstones of molecular biology.
Crick regretted the unusual name of dogma in science later, because he had no intention to formulate a theorem with unumstößlichem veracity. In 1976, he said: "I just did not know what dogma meant. And I could have just as well call center hypothesis ... Dogma was just a catch phrase. "
Types of information transfer
The nine theoretically possible types of transfer of sequential information between DNA, RNA and protein can be divided into three areas according to Crick (1970 ): The general types of transmission happen with rare exceptions in each cell. The existence of specific types of transmission is known, however, done this. Only under specific conditions / in certain organisms The existence of the remaining modes of transmission could not be demonstrated and would refute the Central Dogma today.
- DNA → DNA: Replication
- DNA → RNA: transcription
- RNA → Protein: Translation
- RNA → RNA: RNA replication occurs, for example, in RNA viruses (for example, polio virus), by RNA -dependent RNA polymerases
- RNA → DNA: Reverse transcription occurs, for example retroviruses by the enzyme reverse transcriptase or in eukaryotes by the telomerase
- DNA → Protein: Direct translation from DNA to protein has been demonstrated in vitro in cell-free environments.
- Protein → DNA
- RNA → protein
- Protein → protein
Reception
The central dogma of molecular biology has been criticized since its formulation over again and explained to be obsolete.
In many textbooks, the dogma is, however, not intended by Crick version shown, but in a more restrictive version, which comes from James Watson's textbook Molecular Biology of the Gene, and states that sequential information from DNA to RNA is transferred to the protein and thus only includes the general types of transmission. Although this simplistic version describes the typical sequence of information transfer, but it is understood as a general " dogma " not applicable, as well as Crick remarked. Many " refutations " of the central dogma based on this misunderstanding.
But even against the central dogma in Crick's original version several arguments have been made, including the following: prions were initially suspected as an example of a "forbidden" type of protein -protein information transfer. However, prions are according to the current state of research proteins that can alter the conformation of other proteins and thus transmit any sequential information.
Representative of systems biology emphasize different regulatory feedback mechanisms of proteins to nucleic acids that require it to treat a cell as a complex network in which information transfer sequential nature plays no role emphasized. From this perspective, the central dogma describes only part of the information flow. Criticism is, however, that it is used to justify a reductionist research methodology, the organisms would understand beginning in a bottom- up approach of the genes.