Re: Origin - the wrong word?

From: "Tom Hendricks" <tomhendricks...@xxxxxx>
If you have two replicators (and mine came from the sun acting
like a huge PCR machine on RNA ...)

http://en.wikipedia.org/wiki/Polymerase_chain_reaction
Polymerase chain reaction (PCR) is a molecular biology technique
for enzymatically replicating DNA without using a living organism,
... It requires no more than a test tube, a few simple reagents,
and a source of heat."

Has anyone demonstrated that PCR would work with RNA instead of DNA?

PCR is used to amplify specific regions of a DNA strand. ...
PCR, as currently practiced, requires several basic components. These
components are:
* DNA template, which contains the region of the DNA fragment to be
amplified
* Two primers, which determine the beginning and end of the region
to be amplified (see following section on primers)
* Taq polymerase (or another durable polymerase), a DNA polymerase,
which copies the region to be amplified
* Deoxynucleotides-triphosphate, from which the DNA Polymerase
builds the new DNA
* Buffer, which provides a suitable chemical environment for the DNA
Polymerase

Do you have any reason to expect a prebiotic soup to contain both
primers, any polymerase whatsoever, and a large supply of the four
nucleotides activated to triphosphate?? Any one of those seems
highly unlikely in prebiotic soup. All three together seems totally
contrived, no decent chance it'd ever occur abiotically.

But even if your sun-cycle replicator idea would somehow work, it'd
achieve only one replication cycle per solar day (a few hours
shorter than the 24 hours it is now), whereas temperature cycling
in a convection cell near an undersea geothermal vent could cycle
much faster, allowing copies of that replicator to swamp the feeble
number of copies made by the solar-cycle replicator. With many such
vents around the ocean, there'd be many different convection-cycle
times, hence a wide range of different rates of replication. Some
would be too fast, not allowing enough time for the process to run.
Some would be too slow (like your solar cycle), swamped by the
cycles that were faster but not too fast.

More likely, IMO, during most of the 100-year intervals between
asteroid/comet crashes there didn't happen any successful replicator.
But by chance during one of those intervals a successful replicator
came along, and before the end of that 100-year interval a gazillion
copies of that replicator had been formed, diffusing into all sorts of
crevices. When the next crash occurred, a few of the copies
happened to survive

(2nd fluke needed)

Well, given exponential growth during the between-crash period, the
ocean would be swamped by copies, with copies diffusing into every
accessible crevice, so it doesn't take a fluke for some of those
copies to survive the next crash.

, allowing the replication process to resume
as soon as conditions permitted

(3rd fluke needed)

Well the only not-permitting condition after the comet/asteroid
crash would be the ocean boiled away, and no fluke is needed for
temperature to cool down globally (by simple radiation to space)
and water vapor to condense and re-fill the ocean again.

.. If a really bad crash occurred, destroying the
environment long enough to preclude even one copy of the replicator
surviving, then it might be ten million years before another successful
replicator chanced into existance

(another fluke event)

In my scenerio, I'm assuming the expected time for chance
abiogenesis to produce another capable replicator is on the order
of a few tens of thousands of years, or maybe hundreds of thousands
of years, or even a million years, so after ten million years
surely several capable replicators would have been created and one
or another of them would get lucky and make a few copies before the
original is gone. It doesn't take a fluke for something to happen
during ten million years, if the expected occurance rate is once
per million years or even faster.

... IF life exists the ODDS are it happened easily and often.

But *how* often? Abiogenesis once per ten million years is quite
sufficient for life to have arisen on Earth when it did.
Abiogenesis much more frequently is unnecessary to explain life.

that is what reasonable scientists should be thinking about.

We're trying. But at present there's no demonstration that any RNA
polymerase is spontaneously created from abiotic conditions, so at
present it's not reasonable to claim that RNA polymerase in fact
occurred and was responsible for RNA PCR abiogenesis.

At the very least we can say its 0-100C to allow for
liquid water (though with more pressure you can have slightly
higher temp)

And a few degrees below 0C due to lots of dissolved minerals.
But yes I agree liquid water was very likely necessary.

But once you state that obivous fact, then you have to carry it
through and see that every aspect at least is originally dependent
on the sun heat cycle.

No. That's not a valid conclusion at all. Most of the ocean stays
liquid for millenia yet never undergoes a sun heat cycle.

If you deny this basic then tell me how life can begin outside
of liquid water and outside the HZ, habitable zone of its star.

Now you've switched back again, from sun heat cycle to just
temperature bounds. Can't you see the two are different?

replication leads by itself to nothing but a better replicator.

Agree.

A Spiegelman-like monster would win out.

No. The Spiegelman monster is a parasite upon already-existing
life, not a self replicator.

.

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