Monday, 31 October 2011

The central dogma of molecular biology is toast

It is now clear that the central dogma of molecular biology is toast.

The central dogma of molecular biology was presented as follows by Francis Crick in 1970:

The central dogma of molecular biology deals with the detailed residue-by-residue transfer of sequential information. It states that such information cannot be transferred back from protein to either protein or nucleic acid.
Genetic engineers can now take detailed sequence information from wherever they like, wire it into genomes then and create adult organisms containing the new genes. We can sequence proteins (for example, consider the recent sequencing of dinosaur proteins), recreate the genes that produce them (give or take a little base-pair uncertainty) and then use standard gene-delivery mechanisms to put them into gametes. From there, they can go on to develop into organisms. The central dogma says all that is impossible - so it is simply wrong.

Others have pointed out the inaccurate nature of the central dogma in the modern era. Here's James Gardner (1999):

to a degree that is largely unappreciated by orthodox theoretical biologists, the ongoing revolution in biotechnology renders the central dogma obsolete. The fact is that information can and does flow upstream into the genome

The best defense of the central dogma is probably the claim that genetic engineering is not part of molecular biology. I think that is pretty self-evidently a feeble attempt to salvage an outdated piece of dogma. Molecular biology is the branch of biology that deals with the molecular basis of biological activity. Genetic engineering is "biological activity" and - like most other biological processes - it has a "molecular basis", so: it is part of molecular biology. Anyone sceptical of the idea that genetic engineering qualifies as "biological activity" should check with the definition of biology.

Another possible defense is that the genetic code is redundant, so reverse engineering can't learn exactly what the original codon is from the corresponding amino acid. This defense runs into a technical problem. The central dogma prohibits the flow of detailed sequence information from protein to DNA, from protein to RNA, and from protein to protein. Even if you accept a very strict definition of what "detailed sequence information" means, the central dogma's prohibition of protein to protein information transfer would still have been violated.

Here is Richard Dawkins (2004), defending the central dogma:

In this version the central dogma has never been violated and my bet is that it never will.
Here is Larry Moran (2012), defending the central dogma:

These days, there seems to be a class of evolution critics who are determined to overthrow the Central Dogma as part of their crusade to revolutionize biology. Shapiro falls into that group. It’s not a group you really want to be associated with if you value your intellectual reputation, because its members almost always misrepresent the correct view of the Central Dogma described by Francis Crick in 1958 and 1970. The correct version of the Central Dogma is that once information is transferred from nucleic acid to protein, it can’t flow back to nucleic acids. In other words, translation is unidirectional. The Central Dogma has never been overthrown or seriously challenged. If critics get that wrong, how can you believe anything else they say?
Despite being toast for some time, the central dogma of molecular biology is still in all the textbooks. We know from the history of religion that old dogma dies hard - this is a case in point.


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