Membrane 2nd, Mars Never (Copy)

<[email hidden]> wrote in message
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Quoted message said:

Two separate ideas.

IF I am correct and UV caused pyrimidine dimers was a
selection force that gave an advantage to purine codons
which I associate with mostly hydrophilic amino acids, as
opposed to pyrimidine codons which I associate with mostly
hydrophobic amino acids.

THEN that would favor purine coded hydrophilic amino acid
chemistry. Thus they would have the edge over pyrimidine
coded hydrophobic chemistry.

But that also means that hydrophilic chemical reactions
would probably precede hydrophobic ones.

That would suggest that the naked gene hydrophilic
chemical reactions would probably precede they membrane
hydrophobic chemical reactions.

Membrane forming lipid molecules have both a hydrophobic
part and a hydrophilic part. My OOL scenario assumes that of
the interesting chemical reactions happen in the hydrophilic
part - at least until photo-pigments are invented.

Quoted message said:

Thus this might set up a time line. First the chemistroy
of hydrophilic amino acids would be favored, with the
chemistry of hydrophobic amino acids coming 2nd.

ALSO,

IF UV light is an important selection part of the origin,
and its intensity must be at similar levels as that that
struck earth, THEN Mars is too far out to get that same
UV proponent of life. That would suggest life could not
start there.

The surface of Mars today gets more UV than earth. Back
before earth got its ozone layer, the surface of Mars still
got more UV than does the average surface location on earth
- if you remember that those locations are mostly under
water. And even if you limit yourself to dry land, the UV
photons on Mars are just as strong as on earth - only they
are about 2.5 times less abundant. That is still a lot of
selection against pyrimidines.

<< The surface of Mars today gets more UV than earth. Back
before earth got its ozone layer, the surface of Mars
still got more UV than does the average surface location
on earth - if you remember that those locations are mostly
under water.

For the most part I agree with this post. But the above is a
bit of a catch 22. IF Mars had no water, it may have had
more UV than Earth, but how can life start with no water.

IF it indeed had water, then its UV would be less than Earth
with water too.

By the way, what is your opinion on dimers as being a part
of selection pressure?

And even if you limit yourself to dry land, the UV photons
on Mars are just as strong as on earth - only they are
about 2.5 times less abundant. That is still a lot of
selection against pyrimidines.

"TomHendricks474" <[email hidden]> wrote in message
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Quoted message said:

By the way, what is your opinion on dimers as being a part
of selection pressure?

Tom, as I have said several times, and as several other
people have said, it doesn't even make sense to TALK about
"selection" of entities that do not reproduce.

As a stretch, it MIGHT make sense to talk about selection of
a chemical species that is continually produced pre-
biotically, but nucleic acids don't qualify, IMO. Maybe you
could convince me that the bases are continually produced,
or some simple amino acids, but not polynucleotides.

If we are talking about reproducing naked genes, then maybe
there is some selection due to UV formation of dimers. That
pressure would act against any duplex sequence that has
consecutive pyrimidines. So, it would select for sequences
that alternate between purines and pyrimidines.

More strongly, it would be a selective force encouraging any
nucleic acid sequence that is not completely stupid to get
into the deep water and out of the sun.

"TomHendricks474" <[email hidden]> wrote in message
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Quoted message said:

<< Tom, as I have said several times, and as several other
people have said, it doesn't even make sense to TALK about
"selection" of entities that do not reproduce >>

Well I'm making up a new term called 'zorchtok' It happens
to be a verb, noun, adjetive, etc.

Zorchtok means that what chemicals that play a part in
prebiotic

chemistry, and

Quoted message said:

surivive the environment were likely to continue to be
active chemicals in prebiotic chemistry, and that those
that were altered in a way that made them inactive would
not continue to play a part in

prebiotic

Quoted message said:

chemistry.

Now, whenever I incorrectly say selection (or chemical
selection) please translate as zorchtok the correct term.

IMO it doesn't make sense to talk about zorchtok for nucleic
acids. Zorchtok keeps your polynucleotide intact for a few
years, rather than a few days, say. It still is destroyed
long before it can "evolve" into something. Just how many
years of zorchtok are you talking about here before your
molecules "learn" how to reproduce?

Perplexed in Peoria <[email hidden]> wrote or quoted:

Quoted message said:

"TomHendricks474" <[email hidden]> wrote in
message

Quoted message said:

Quoted message said:

By the way, what is your opinion on dimers as being a
part of selection pressure?

Tom, as I have said several times, and as several other
people have said, it doesn't even make sense to TALK about
"selection" of entities that do not reproduce.

It does make *some* sense.

Selection is normally all about choosing.

To give an example, lighning can selectively strike and
destroy tall objects regardless of whether they self-
reproduce or not - and that's a type of selective process.

What isn't possible without reproduction is evolution and
life.
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