Central dogma of molecular biology

From Conservapedia

Jump to: navigation, search

The central dogma of molecular biology refers to the flow of sequential information from DNA to RNA to protein within a cell via the processes of transcription (DNA to RNA) and translation (RNA to protein)[1].

The hypothesis (later demonstrated to be true) that DNA encoded for specific protein sequences via an RNA intermediate is generally credited to Francis Crick, who published a review article describing this hypothesis in 1958.

Although this process is referred to as "dogma", it is important to emphasize that modern molecular biology has demonstrated many instances in which the flow of sequence information is not linear or unidirectional. For instance, RNA can be copied into DNA, this is called reverse transcription, and there are even instances of proteins acting directly on DNA sequences without the need for any intermediates.

Additionally, any discussion of gene function must bear in mind that regulation of gene expression (defined as the production of a functional gene product) occurs at every level of the process. Therefore, it is often helpful to consider information flow as a dynamic function of cell homeostasis, instead of a fixed process.

General Mechanism

1. RNA polymerase synthesizes a precursor RNA transcript that is complimentary to the "template strand". The DNA template is read in the 3' to 5' direction, the transcript is synthesized in the 5' to 3' direction.

2. 5' gaunalyl cap is cotranscriptionally added to the nascent transcript, the 3' poly-A tail is added post-transcriptionally, and the precursor RNA is spliced into mRNA.

3. The mature mRNA is exported from the cell nucleus into the cytosol.

4. The mRNA binds to a ribosome. Translation begins.

5. Translation proceeds as tRNAs complement the codons in the mRNA, and bring individual amino acids to grow the polypeptide. Polypeptide synthesis occurs in the N-terminal to C-terminal direction.

6. When translation is complete, the new polypeptide is folded into its final conformation. Depending on the protein, post-translational processing may occur before the protein is "mature".

References

  1. Weaver, Robert F. Molecular Biology. 4th ed. Boston: McGraw-Hill, 2008.
Personal tools