Re: Crystalline ancestry: Vegetative growth

Perplexed in Peoria wrote:
"Tim Tyler" <seemysig@xxxxxxxxxxxxxx> wrote:
"Perplexed in Peoria" <jimmene...@xxxxxxxxxxxxx> wrote:
"Tim Tyler" <seemy...@xxxxxxxxxxxxxx> wrote:

-http://originoflife.net/vegetative_growth/
Interesting. The pictures of crystal-structure-models were very
helpful, but I have to complain that you didn't have pictures for
the heart of this presentation - the 1-D of information crystal,
which can have multiple genotypes in a single crystal. So,
I am not really sure what such a beastie or colony of beasties
would look like.
The front of the AGCS paper has a picture of one type:

http://originoflife.net/vegetative_growth/graphics/agcs.png

It looks like seaweed.

Pretty picture, but I simply cannot imagine how it applies
to the subject under discussion.

Well, that is what some of these crystals are thought to look
like. I am not clear exactly what you are asking, but this:

"Indirect support for this kind of faithful sideways
copying comes from a phenomenon sometimes seen in layer
crystals where some complex random-looking block of
layers is repeated several times, one on top of the
other. Examples of this come from mixed-layer materials.
Although formed at high temperatures, barium ferrites
have provided some especially dramatic cases. For example,
Kohn et al. (1971) found a 526 =C5 repeating sequence of
37 layers, while in another study McConnell et al. (1974)
found an 841 =C5 sequence of 59 layers. Each of these
groups remarked that limitations of their (different)
electron microscope techniques may have prevented even
longer repeating sequences from being found. Clay
minerals frequently have mixed-layer structures and often
show (more modest) sequence repeats (Reynolds 1986).
There is a similar story with polytypes, e.g., silicon
carbide (Verma and Krishna 1966) and micas (Baronnet 1980;
Baronnet and Kang 1989).

The classical explanation for such repeats (Frank 1951)
is that the crystals would have grown through addition of
units to edges that are exposed on the surface due to a
deep screw dislocation. An alternative less tidy
mechanism has been suggested more recently (FIG. 3) to
explain the long repeats found in barium ferrites (Turner
et al 1996). This =93seaweed growth=94 mechanism also depends
on faithful sideways addition of units. A similar
mechanism might apply to other cases of long c-axis
repeats."

Page 33 of this PDF:

- http://www.elementsmagazine.org/Elements_online/ELEM_V1n3.pdf

.....might help - as might an examination of the associated
micrograph of a "seaweed-like" illite.

As for "multiple genotypes" it is easy to imagine mutations.

Not for me. At least not when you have different genotypes
on different facets of the same crystal. And particularly
not when the information is carriied by a 1-D sequence
of layer orientations or compositions.

Mutations are ubiquitous in modern biology. It doesn't
take much to cause mutations - cosmic rays, mechanical
jolts, unintended chemical reactions, electrostatic
charges, stress. Mutations are everywhere.

The problems with mutations in origin of life scenarios all
involve preventing them from happening too much.

You seem to be wondering how they could happen at all. That
is *really* not a problem. It is the most primitive creatures
ever which are under discussion here. They would have some
of the most pathetic error-correction technology ever seen
in a living organism - and would be some of the most
vulnerable to mutations.

If mutations are difficult, that is great - a huge plus
point. The real problem is the other way - showing that
mutations can soometimes be infrequent enough for adaptations
to arise and persist.
--
__________
|im |yler http://timtyler.org/ tim@xxxxxxxxxxx Remove lock to
reply.

.