>>> pvh at egenetics.com 02/21/01 04:34AM >>>
>
>
> Peter said in his post: "Finally, I think Gould is pretty much right in
> spirit, but makes
> a couple of logical mistakes in setting forth his argument. I.e. I think
> we pretty much know that 'information' resides in the way molecules
> interact (i.e. some 'noise', e.g. a mutation in a gene, does not
> necessary lead to loss of cellular 'information' - i.e. preservation
> of state and function) rather than flowing one way from some 'low level'
> set of molecules to some 'high level' ones. But I think the way he sets
> forth his argument is journalistic, rather than drily logical, and he
> could be faulted if judged on strict logical grounds."
>
> Charles: Is there anything in the genome project that contradicts the Central Dogma as articulated by Crick ? :
>
> "In 1957. Francis Crick, one of the co-discoverers of the importance of the genetic molecule DNA, called this hypothesis, the "Central Dogma" which :
>
> "Stated that once "information" has passed into protein it cannot get out
> again. 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."
>
Hm. There's a step missed out there - DNA to RNA.
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CB: Aren't both DNA and RNA nucleic acids ( The "N" stands for "nucleic" and the "A" stands for "acid",no) ? Thus, the reference of transfer of info from nucleic acid to nucleic acid would include the step DNA to RNA .
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And yes, well, that version of the Central Dogma has fallen prey to evidence years ago, with the discovery of retro-viruses (e.g. HIV), which splice their genetic material into DNA - i.e. information in the viral proteins quite literally gets into DNA.
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CB: I thought viruses were bits of DNA or nucleic acid in protein cases. And that viruses put their DNA, nucleic acid , not protein, into the host cell. That would still be nucleic acid to nucleic acid.
If so, What is fallacy or weakness of practice in the following idea ?
Shouldn't DNA sequencing make it a faster track to figuring out how to disarm incurable viruses ,such as HIV ? Sequence the DNA in the virus, and then synthesize a medicine that has a marker for the virus based on some unique sequence ;and that same medical molecule substitutes itself somewhere in the DNA of the virus and changes the sequences of the virus DNA so that the virus DNA cannot use the machinery of the host's cells to replicate the virus ???
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Also, the fact that regulatory networks control gene expression (which gene is 'switched' on - generally about 10% of genes are 'switched on' in any cell, as I recall), and the fact that the process of going from DNA to protein is complex, with many steps where intermediate steps get 'tweaked' (e.g. DNA is transcribed into RNA in a complex fashion - multiple different RNAs can be created from one gene. Also, there is 'post-translation' modification, which happens after RNA is translated into protein - but I don't know much about that) seems to me to be at odds with the CD - proteins and RNAs are involved in altering the information flow - to what extent this 'alteration' makes the whole CD thing much less useful as a model is a subject of debate. I tend to think the CD simply captures one process amongst the many processes which 'conserve information' in cells - others differ.
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CB: Uh huh. I'm wondering about the "regulatory networks". This sounds like a reference to a process that might involve info flow from proteins to DNA , violating the dogma as stated. As far as I can tell, it does not involve modifying the genes, but switching them on and off.
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Also, I don't really see it as 'genome project' results which are challenging the CD here - a lot of the research going into the comments I'm making didn't happen as part of the Human Genome Project.
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CB: Yes, I was just going to say that those seem to be challenges to the CD, but not from the results we just heard reported, but from prior research.
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>
> Doesn't the result of fewer genes than expected, mean that the genotype is
> less detemining of phenotype than those who expected more genes thought,
I guess you could read it that way - if there was a 1-to-1 gene-protein link, you'd possibly have grounds for arguing that the gene expression process was straightforward and not a big influence on the information content on the cell. *In practice*, I haven't come across any real life scientists who argued that there was a 1-to-1 gene-protein link, certainly not at this stage of the game.
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CB: Did any biologist ever argue that there were no environmental causes intervening between genotype and phenotype ? Isn't there something of a straw biologist being knocked down ?
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> and that post zygotal environment plays a bigger role, but not that
> phenotype and experience cause changes in the genotype other than randomly
> with respect to adaptation to that phenotype or experience ? There is no
> contradiction of the socalled Central Dogma in the genome project results ,
> or do we reinvestigate Lysenko ?
Lysenko's arguments, as I've heard them laid out, involved not just post zygotal environment playing a role, but also the inheritance of acquired characteristics.
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CB: Yes. I thought "no inheritance of acquired characteristics" was equivalent to the Central Dogma.
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If we didn't believe that post zygotal environment played a role, we wouldn't have a science of plant breeding - we could probably do to a have a more nuanced science like that (e.g. examining companion planting on a large scale), but I hardly think a return to Lysenko is on the agenda.
Peter -- Peter van Heusden <pvh at egenetics.com> NOTE: I do not speak for my employer, Electric Genetics "Criticism has torn up the imaginary flowers from the chain not so that man shall wear the unadorned, bleak chain but so that he will shake off the chain and pluck the living flower." - Karl Marx, 1844 OpenPGP: 1024D/0517502B : DE5B 6EAA 28AC 57F7 58EF 9295 6A26 6A92 0517 502B