Simon Wrote:
-------------------------------------------------------
> bernard Wrote:
> --------------------------------------------------
> -----
> >
> > These say nothing about human females being
> more
> > different from human males than humans from
> chimps
> >
>
>
> Its more related to statistics than anything else
> (isn't it always), but it was a story I read
> somewhere that was probably derived from this kind
> of thing;
>
> [www.thetech.org]

Quoted from this web site:


So is the bottom line that men and male chimps have more in common than men and women? Of course not. If we take a closer look, we see some of the dangers of looking at raw percentages instead of individual changes.


>
>
> > >
> > > Okay but its if we don't know half of
> what
> > prions
> > > do in humans then there is a possibility
> it
> > could
> > > be similar ?
> >
> > No. Prions in humans produce deadly diseases.
> We
> > are not yeasts
> >
>
>
> No. It is now commonly accepted that prions
> perform VITAL roles in humans, especially in the
> nervous system. I can find plenty of references
> to this if you like.
I doubt it. Remember that the PROTEIN itself is present in the nervous system but I would wager that the ueful cnformation is not the prion conformation. I'm sure that some prions are useful in some organisms-- but VITAL to humans?
From WIKIpedia:

"Prions - short for proteinaceous infectious particle - are infectious self-reproducing protein structures. Though their exact mechanisms of action and reproduction are still unknown, it is now commonly accepted that they are responsible for a number of previously known but little-understood diseases generally classified under transmissible spongiform encephalopathy (TSEs) diseases, including scrapie (a disease of sheep), kuru (found in members of the cannibalistic Foré tribe in Papua New Guinea), and bovine spongiform encephalopathy (mad cow disease). These diseases affect the structure of brain tissue and are all fatal and untreatable.
>
> It is incorrect behaviour of prions that causes
> diseases.
No it is PRECISELY the formation and the fact that they induce the normal conformation of the base protein to polymerize that causes the disease.

Just like it would be wrong to say that
> DNA causes cancer....
No exactly, but the machanism that takes place in cancer is that the regulatory mechanism that stops cells from reproducing is turned off-- A better example for you of "activation" of a gene.
>
>
> >
> > This is a very slippery use of semantics.
> the
> > problem is using words in their "everyday"
> meaning
> > when applying to a scientific concept withg
> a
> > precise meaning. Of course, any time a cell
> makes
> > a protein it can be said to be "activated"
> but
> > that is NOT the meaning used in genetics.
> > "Activated" implies that there are on/off
> > positions concerning the particular
> expression (a
> > better term actually) of a gene. This on/off
> > switch will be "activated" under particular
> > conditions BY ANOTHER gene which is the
> controller
> > of the first. Do you see an essential
> difference
> > both in your example above and in the case of
> the
> > prions?
> >
>
>
> Okay yes I do, but we've got sidetracked due too
> my general ignorance of the subject with regards
> to what term is appropriate in different
> circumstances. The fact is that something is
> different in the yeast in the way it deals with
> environmental factors after sexual reproduction.
> And that must be relevant to evolution, despite
> the fact we're looking at a smaller aspect of it
> which is not strictly genetic.
>
>
> > >
> > >
> > > > What is produced is the
> > > > equivalent of producing mutations
> at a
> > rate
> > > higher
> > > > than would be normally expected.
> > >
> > >
> > >
> > > Are you saying this is all Lindquist is
> > claiming
> >
> > Yes for that part of the experiment. her big
> news
> > is the transmissiion of the prion state for
> > Sud35.
>
>
> Transmission of factors relating to mechanism of
> genes to creature = factor in evolution, surely ?

But I keep telling you that the trasmission is the ability to make prions. Yes, it is all related to evolution but I don't think it merits much discussion.
>
> > >
> > > Okay I will read up a bit more on the
> but
> > could
> > > you clarify whether you rekon I've got
> this
> > wrong.
> > > When the first generation of yeast
> were
> > first
> > > exposed to this disease they didn't
> produce
> > this
> > > protein that protects them,
> >
> > There was NO exposure to a disease. It was a
> > condition of low concentrations of Hsp104
> (heat
> > shock protein 104] that led to a
> conformation
> > change of Sud35 to a priion. High
> concentrations
> > of the absence of Hsp104 reversed the prion
> > condition.
> >
> > The prion formation and its subsequent
> > transmission was not a CURE for the cause of
> the
> > prion. What it did is that the condition
> allowed
> > the yeast to make more mutants than would
> have
> > been the case AND some of the se mutants
> provided
> > some advantage against paraquat--- a
> substance
> > that had nothing to do with the formation of
> the
> > prion in the first place.
> >
>
> If thats the case then why did New Scientist
> claiming a Lamarckian aspect to it ?
Their claim to "Lamarckian" has to do with the transmission of ability to make prions-- you really need to get off the subsequent mutations-- that is routine once you disrupt the Sud35 function by making it a prion.


I certainly
> don't consider them any kind of foundation of
> truth (as you know ) But if they spun a dodgey
> weave like that then thats just not cricket!
>
>
> >
> > then when the next
> > > generation was 'born' (from the ones
> that
> > had
> > > developed resistance) they instantly
> produced
> > this
> > > protein that gave protection ?
> >
> > No protection against the cause of the prion.
>
>
>
> I thought part of it was that the prion developed
> in the first place as a reponse to the disease ?
Read the paper!!!! I gave you a summary of the other relevant paper above -- I repeat the paragraph

"In the case of the yeast in question, as I understand it- There is a protein Sup35 that ordinarily is in a soluble conformation in this condition the gene is said to be [psi -]. when this condition exists the function of Sup35 is to stop the gene's transcription machinery from transcribing the DNA of non-coding DNA. {You were partially right, and I was partially wrong. Non-coding DNA IS involved, but it is not involved in the genetic transmission of the prion). There is also the involvement of another protein Hsp104 in the process. If Hsp104 is present at low concentrations, it will catalyze a change in the conformation of Sup35 to an amyloid-like polymer-- a prion. The cell in this condition is [PS1+]. When this happens, the normal functioning of Sup35 ceases and [PS1+] cells start to transcribe DNA from the non-coding DNA sections. This is what produces the "mutations" that in 20% of the time confer resistance to paraquat. In nature the appearance of [PS1+] is a transient occurrence that occurs spontaneoously about once every million cells . If Hsp104 is present at high concentrations or absent altogether, the conversion to prion does not occur."

The paper is

Science. 2004 Jun 18;304(5678):1793-7. Epub 2004 May 20.

Hsp104 catalyzes formation and elimination of self-replicating Sup35 prion conformers.

Shorter J, Lindquist S.



> What convinces you this is not the case ?
>
>
> > This
> > is NOT a cure for prions
>
>
> Are you claiming any creature could survive
> without prions ?

Where do you get the idea that all living thing have to have prions to exist? Remember prion is one conformation of a protein. The other conformation coould be the essential form and the prion conformation the aberrant.

If not then how could you have a
> "cure" for prions ?
>
>
>
> > -- it is just a way to get
> > faster mutations. YOu could get the same
> result by
> > subjecting the yeast to a lot of
> radioactivity---
> > but that would be completely uninteresting
> > genetically.
> >
>
>
> I rekon you're glossing over the significance, but
> I do readily admit you have a better grasp of this
> subject in general and I'm learning stuff along
> the way
>
> Simon
>


Bernard