One of my pet peeves is the misuse of the term "Central Dogma of Molecular Biology" [Basic Concepts: The Central Dogma of Molecular Biology]. Most people define it as the flow of information from DNA to RNA to protein. Many then go on to declare that the Central Dogma has been overthrown because of reverse transcriptase, alternative splicing, microRNA, epigenetics, or whatever.This month's issue of SEED has a tear-out summary (cribsheet) of "Genetics." In one of the boxes titled "The Central Dogma of Molecular Biology" there's a drawing of the major pathways of information flow. The caption says.
There are nine ways information can theoretically flow between DNA, RNA, and protein. Of these, three are seen throughout nature, DNA to DNA (replication), DNA to RNA (transcription), and RNA to protein (translation). Three more are known to occur in special circumstances like viruses or laboratory experiments (RNA to RNA, RNA to DNA, and DNA to protein). Flows of information from protein have not been observed. The trend is clear: information flow from DNA or RNA into protein is irreversible. This is known as the "central dogma," and forms the foundation of molecular biology.Yeah! As far as I know this is the only popular magazine to get it right.
12 comments :
So, the shades of Lamarckism continue to haunt biology and the occasional 'sightings' are made, even by professional biologists from what I hear. What does all this fuss about epigenetics add up to? 'The central dogma of molecular biology' peeves you? I bet! - just as much calling atheism ‘your central dogma’ I suppose!
Dogma has such a sordid religious history and retains all kinds of negative connotations.
Principle would more appropriate.?
I agree with Gerald: "dogma" is definitely a misleading word. Let's get rid of dogmas of any kind! (Oops, isn't that dogmatic)
I agree with Larry- even people who should know better often get that wrong, so it is indeed surprising and heartening to see a popular science magazine get it right.
IANAB, but I'm not sure there is anything forbidding Lamarckism or its "shades" as a viable mechanism, they just aren't major ones. I suspect a reason why it isn't observed, as well as that basic plasticity is constrained, would be for reasons of stability and reproductive power - they could be out-selected (failures from change problems) and out-reproduced (copy problems). Perhaps especially in the case of the evolutionary power of sex.
Feel free to speculate how a biosphere would look if it operated in a lamarckian regime. And how much shades of lamarckism (imperfect replication?) do you think the posited RNA world could handle?
Interesting and perhaps useful question Torbjorn - I'm speculating right now!
... a few quick speculations later
Torbjorn: you suggest (or suspect) that only a small level of lamarckism could be tolerated for survival reasons. Perhaps. However I suspect there is also another rather fundamental factor: the logical complexity of the mechanism that would be required to feed phenotypic layouts back into genetic 'data' - it suggests a system that 'learns' by a rather more direct route than trial, error and (for pluralists) random possibility as does conventional evolution.
...hhmm.. bit like asking the cake to write the recipe perhaps!!
... in fact the required recipe may be unrecoverable from the cake - that is, the process is irreversible because info. is lost in creating the cake. (algorithimic irrevesibility and all that)
(I wish you hadn't raised this one Torbjorn .. my mind keeps coming back to it and I'm supposed to be getting on with the cleaning!)
..come to think of it, I bet someone somewhere has thought of all that...
Thimothy: I think the complexity is pretty much that would be the problem when making copies, it would take more resources and time.
Besides, the code working against the Central Dogma, taking information from proteins back into DNA (or their analogs) would need to be 1-1 as you note. In fact, it seems Hubert Yockey noted that the dogma is a mathematic consequence of the evolved system. I think Gert Korthof's illustration in the link shows how much Yockey missed and why such systems are unlikely to occur.
Thanks for the link Torbjorn. It's certainly relevant to the issues I was thinking about above, so thanks.
I wonder what Larry thinks of this kind of thing!!!!
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