Central Dogma

Francis Crick developed the “central dogma of molecular biology” in the 1960s.
It states that information flows one way: from DNA to protein.
- DNA codes for the production of RNA (transcription).
- RNA codes for the production of protein (translation).
- Proteins do not code for the production of protein, RNA, or DNA.
In Crick's own words, Once information has passed into protein it cannot get out again. In more detail, the transfer of information from nucleic acid to nucleic acid, or from nucleic acid to protein may be possible, but transfer from protein to protein, or from protein to nucleic acid is impossible.
Note: the central dogma has been challenged.
- We will talk about how in the next chapter.

Figure 12.2, Purves's Life: The Science of Biology, 7th Edition

Translation Details: Polysomes (Polyribosomes)

A polysome consists of ribosomes and their growing polypeptide chains moving in single file along a mRNA molecule.
Note: the pictures below must be of a bacterium, not a eukaryote, since there is no post-transcriptional modification of the mRNA.

Figure 12.13, Purves's Life: The Science of Biology, 7th Edition; Figure 17.20, page 311, Campbell's Biology, 5th Edition

Some antibiotics inhibit protein synthesis in bacteria to fight off the infection.

Antibiotic	Step Inhibited
Chloromycetin	Formation of peptide bonds
Erythromycin	Translocation of mRNA along ribosome
Neomycin	Interactions between tRNA and mRNA
Streptomycin	Initiation of translation
Tetracycline	Binding of tRNA to ribosome

Figure 12.3, Purves's Life: The Science of Biology, 7th Edition; Figure 17.23, page 315, Campbell's Biology, 5th Edition