>>> pvh at egenetics.com 02/23/01 05:00AM >>>
On Thu, Feb 22, 2001 at 01:41:49PM -0500, Charles Brown wrote:
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> >>> pvh at egenetics.com 02/21/01 04:34AM >>>
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> 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 .
I guess it could be...
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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.
Most viruses put their DNA or RNA into the host cell, and wait for the transcription/translation machinery to turn it into new viral proteins.
Retro-viruses put their nucleic acid into the host DNA - and the
viral proteins do the job of putting it there. Those viral proteins
seem to be pretty much violating the Central Dogma.
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CB: I see.
So, the retro virus proteins send a message to the host cell DNA telling it to print out retro virus proteins, violating the part of the dogma as formulated by Crick which says no protein to nucleic acid messages ?
However, the message to the host cell DNA from the retrovirus protein does not change the host cell DNA itself. That would be required for violating the dogma against Inheritance of Acquired Characteristics. It might even have to be that the protein changes gonadal cells in a way that directly impacts the way the next generation of offspring respond to this specific protein and virus, this specific aspect of the environment to violate the "no IAC" dogma?
I wonder if the difference between the central dogma as stated by Crick and violation of Inheritance of Acquired Characteristics dogma might be this as I just said.
However, we are talking retroviruses. No violation of either dogma by evidence from human genome project ,no ?
> If so,
> What is fallacy or weakness of practice in the following idea ?
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> 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 ???
This is exactly what some modern anti-viral treatments are aimed at. I can't recall the exact details right now, but one new treatment is aimed at degrading the protein used by HIV to grapple onto the cells it wants to infect. Sequencing viral DNA/RNA is important for research in these fields, although you need to then go on and model the 3D structure of viral proteins. Research in the lab I work at (SANBI) is focussing on examining where mutations in e.g. pathogens such as Plasmodium falciparum (the parasite responsible for malaria) occur - this should give us a handle on how the organism is responding to evade the host immune system / drugs. Mapping the sites of common mutation to a 3D model of the proteins produced gives you an idea of exactly what molecular mechanism for virulence is, which gives you a handle on how to make a better drug. (At which point the lab probably ends up selling this information to GlaxoSmithKline for megabucks, and the resulting drug is sold back to the South African health service for even more megabucks....)
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CB: I hate capitialism.
I know what I was thinking, but didn't say. Does the sequencing of the _human_ genome give some potential insight as to where the viruses are plugging into the human host cell DNA or RNA to replicate, another point at which the viruses process might be stopped ? This would be something from the recent news and project that might help the work of the type you are doing.
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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.
Nope, no modfication of genes, at least as far as I know. But, the CD is specifically talking about 'information' flow, so I think it is valid to argue that the conservation of information in "regulatory networks" is an argument against taking the CD literally.
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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 ?
Yes, I think it is a straw biologist - but unfortunately, the 'popular perception' of genetics resembles this straw biologist a bit, thanks largely to how science is reported in 'popular science' magazines and the general media. Peer review isn't perfect, but it does keep the stuff in Science and Nature at least a little bit less ridiculous than it could be - the most outrageous things are generally kept to the Letters page, or some journal like the Journal of Evolutionary Psychology (used to be the Journal of Socio-Biology). Things seems a bit better in biology than they are in economics, I think.
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CB: Oh yes , I forgot about the evolutionary psychologists. ( how could I ?).
The evolutionary psychologists seem to do a poor job of choosing phenotypes.
Seems that there are phenotypes that are significantly genetically determined, but there are many "phenotypes" that are not.
The position of racist genetic determinists was further refuted by the human genome project. It is not that skin color, hair tecture or shape of facial features are not significantly genetically determined. It is that these genes are 1) not correlated with other genes, 2) let alone other phenotypes which may not be in the category of phenotypical characteristics that are significantly genetically determined. The genome project bolsters the 1) category of arguments against "genetic" racism, and therefore all biological based racism.