Simon Wrote:
-------------------------------------------------------
> bernard Wrote:

>
>
> >
> > This (and the other examples being pursued)
> > resemble the strategy involved in our immune
> > systems. Instead of developing a
> one-gene-one
> > mutation-one disease approach, what the body
> has
> > developed is a a generalized disease
> fighting
> > machinery. The immune system is set up to
> fight
> > any foreign substance (above a threshold
> size)
> > that enters the body. it is extremely
> flexible and
> > self programmming.
> >
>
>
> So is DNA itself. Why do you seperate the
> abilities of the evolution of DNA from the process
> of evolution ? Surely evolution theory as a whole
> does not make such a distinction in such a
> specific way. If it does, and yet has such a
> primitive understanding of the process, such as
> mapping genome to production of specific function
> and even more so feature, then it seems like
> guesswork is taking president over evidence.

I guess it is my failure to communicate. It is all part of evolution. I don't know is my point was that big a point. Essentially it was that in the process of generating the variety that then can be selected by interaction with the environment the DNA of organisms has not been limited to just making "silver-bullets", i.e. an allele that deals with only one selecting factor. Using the example of human disease as the stressor: the sickle cell gene, or thalassemia are specific mutations that respond to malaria. Humans also have a generalized multi-factorial, multi-gene machinery, the immune syatem, that can respond to a myriad of diseases. The immune syatem can respond physiologically to confer lifetime immunity to particular disease organisms but this specific immunity is not inherited. Only the immune system itself is inherited.

>
>
> > The same applies to the development of
> mutation
> > developing machinery. Instead of just doing
> one
> > mutation at a time. Here the DNA codes for a
> > machine to generate mutations that kicks in
> when
> > the organism is under stress. This is still
> > controlled by genes , is Darwinian and does
> not
> > oveerturn the new synthesis.
> > Bernard
> >
>
>
> So you disasociate the fact DNA has evolved the
> ability to generate these mutations with the
> result of these mutations. Are you a closit
> creationist ????
>
> LOL
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.

What I'm still not clear on and need to look at exactly how the authors prove the inheritance of the ability to make prions by daughter cells that did not have the ability originally. The claim is that this is not a transmission through DNA but rather by protein-to-protein. But, in my opinion, it might really be transmission of codes regulating the levels of Hsp104 protein.


Back to your point above. What I'm saying is that the production of proteins coded by the "non-coding DNA section" due to the disruption of Sup35 function and the subsequent responses to paraquat is analogous to the production of specific antigens (which are proteins just like the ones in the yeast except these are exquisitely tailored to the antobody in question) to measles by the immune system. We would not call the production of antigens to measles a "mutation" or even a "dormant gene" because that is just the carrying out of a programmed function. The relevant evolutionary process is the one that led to the development of the immune system itself. In the case of the yeast, the relevant evolutionary process to look at is what Lindquist and I are focusing on-- the mechanism through which the function of Sup35 is disrupted by conversion into a prion, which makes the cell produce a scattershot of new proteins, and how this system is passed on to other generations.

Bernard