In biochemical genetics, the molecular direction of information flow is invariably from DNA→RNA→protein. In other words, DNA is first transcribed into RNA, which then may be translated into polypeptides that make up proteins. This view was so ensconced in the field that it had become known as the “central dogma” (Crick, 1970) of molecular biology.
enzyme; reverse transcriptase
In biochemical genetics, the molecular direction of information flow is invariably from DNA→RNA→protein. In other words, DNA is first transcribed into RNA, which then may be translated into polypeptides that make up proteins. This view was so ensconced in the field that it had become known as the “central dogma” (Crick, 1970) of molecular biology.
Researchers showed that biochemical information could also flow from RNA→DNA. The key discovery came when Howard Temin and David Baltimore, working independently and on different viral systems, identified an enzyme (reverse transcriptase) that catalyzes the conversion of RNA into DNA, thus enabling the passage of genetic information in a direction contrary to the central dogma.
Temin and Baltimore shared the 1975 Nobel Prize for their discovery, testifying to the scientific impact of their work. Today, reverse transcriptase is widely used in the biotechnology industry and in molecular genetics laboratories around the world. Reverse transcription is also recognized to play important biological roles in cells. For example, many transposable elements (see Chapter 24) replicatively transpose from one chromosomal site to another via an RNA intermediate that is reverse transcribed; so too do many “processed” pseudogenes (see Chapter 68). Indeed, processed pseudogenes are a major subclass of pseudogenes typically recognizable precisely because they derive via reverse transcription from a mature messenger RNA from which the intervening sequences or introns (see Chapter 49) already have been spliced out by the cell.
To my knowledge, no one has firmly documented the natural flow of biochemical genetic information from protein→RNA. Thus, at least this portion of the central dogma appears to remain intact. As an interesting footnote to this story, Francis Crick later expressed regret that he had used the word “dogma” in this scientific context, because the word technically means “belief that cannot be doubted” (which by definition would place any dogma outside the purview of science).
1. Baltimore D. RNA-dependent DNA polymerase in virions of RNA tumour viruses. Nature. 1970;226:1209–1211.
2. Crick FHC. Central dogma of molecular biology. Nature. 1970;227:561–563.
3. Temin HM, Mizutani S. RNA-dependent DNA polymerase in virions of Rous sarcoma virus. Nature. 1970;226:1211–1213.
4. Weiner AM, Deininger PL, Efstratiadis A. Nonviral retroposons: genes, pseudogenes, and transposable elements generated by the reverse flow of genetic information. Annu Rev Biochem. 1986;55:631–661.