Scientists Discover Possible Building Blocks of Ancient Genetic Systems in Earth's Most Primitive Organisms

[Mike Painter]

" Scientists believe that prior to the advent of DNA as Earth's
primary genetic material, early forms of life used RNA to encode
genetic instructions. What sort of genetic molecules did life rely on
before RNA?
The answer may be AEG, a small molecule that when linked into chains
forms a hypothetical backbone for peptide nucleic acids, which have
been hypothesized as the first genetic molecules."

http://tinyurl.com/a46c2jo

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0049043

These molecules follow simple chemical rules for formation.
No gods need apply.
--
"When one person suffers from a delusion it is called insanity. When many people suffer from a delusion it is called religion." ~ Robert Pirsig

[pnyikos]

On Nov 11, 3:47�pm, Mike Painter <mddotpain...@sbcglobal.net> wrote:
> " Scientists believe that prior to the advent of DNA as Earth's
> primary genetic material, early forms of life used RNA to encode
> genetic instructions. What sort of genetic molecules did life rely on
> before RNA?
> The answer may be AEG, a small molecule that when linked into chains
> forms a hypothetical

Why hypothetical? Have they been unable to produce PNA from it?

> backbone for peptide nucleic acids, which have
> been hypothesized as the first genetic molecules."

Yes, by Leslie Orgel and others. But that brings up the problem of a
"RNA/DNA takeover" to add to the already knotty problem of how the
"protein takeover" took place.

> http://tinyurl.com/a46c2jo
>
> http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.00...

A news article, shedding no real light on the questions I pose here.
On the other hand, it does include a bit of encouragement to me to
pursue the angle that the beginning of life ON EARTH may have been due
to seeding by an intelligent species ca. 4 billion years ago. The
article says:

"Cyanobacteria sometimes appear as mats or scums on the surface of
reservoirs and lakes during hot summer months. Their tolerance for
extreme habitats is remarkable, ranging from the hot springs of
Yellowstone to the tundra of the Arctic."

This would make them ideal candidates for "seeding" earth by a
technologically advanced [though hardly beyond our present technology,
perhaps] , a.k.a. directed panspermia.

> These molecules follow simple chemical rules for formation.
> No gods need apply.

The real issue is whether this is a feasible part of a path to life
as we know it [not counting viruses]. Any biochemists in the house
who can speak to this?

Peter Nyikos
Professor, Dept. of Mathematics -- standard disclaimer--
University of South Carolina
http://www.math.sc.edu/~nyikos/
nyikos @ math.sc.edu

[Mike Painter]

On Mon, 12 Nov 2012 06:38:34 -0800 (PST), pnyikos
<nyi...@bellsouth.net> wrote:

>> http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.00...
>
>A news article, shedding no real light on the questions I pose here.

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0049043

I just posted a couple links, the second one appears to be more
detailed but apparently got cut.
If this second one is also shortened, "Fjournal.pone.0049043" is the
end of it.

[Steven L.]

On 11/12/2012 9:38 AM, pnyikos wrote:
> On Nov 11, 3:47 pm, Mike Painter <mddotpain...@sbcglobal.net> wrote:
>> " Scientists believe that prior to the advent of DNA as Earth's
>> primary genetic material, early forms of life used RNA to encode
>> genetic instructions. What sort of genetic molecules did life rely on
>> before RNA?
>> The answer may be AEG, a small molecule that when linked into chains
>> forms a hypothetical
>
> Why hypothetical? Have they been unable to produce PNA from it?
>
>> backbone for peptide nucleic acids, which have
>> been hypothesized as the first genetic molecules."
>
> Yes, by Leslie Orgel and others. But that brings up the problem of a
> "RNA/DNA takeover" to add to the already knotty problem of how the
> "protein takeover" took place.

If (as we discussed in an earlier thread), RNA/DNA was an advantageous
carrier of genetic code information, then there could have been a number
of precursors: PNA, polycyclic aromatic hydrocarbons (PAHs), perhaps
others, all trying to survive and multiply and evolve. And then a kind
of "convergent evolution" took place, where all these different
biochemical evolutionary paths all eventually ended up at the same
place: RNA.




--
Steven L.

[pnyikos]

On Nov 12, 7:02�pm, "Steven L." <sdlit...@earthlink.net> wrote:
> On 11/12/2012 9:38 AM, pnyikos wrote:
>
>
>
>
>
>
>
>
>
> > On Nov 11, 3:47 pm, Mike Painter <mddotpain...@sbcglobal.net> wrote:
> >> " Scientists believe that prior to the advent of DNA as Earth's
> >> primary genetic material, early forms of life used RNA to encode
> >> genetic instructions. What sort of genetic molecules did life rely on
> >> before RNA?
> >> The answer may be AEG, a small molecule that when linked into chains
> >> forms a hypothetical
>
> > Why hypothetical? �Have they been unable to produce PNA from it?
>
> >> backbone for peptide nucleic acids, which have
> >> been hypothesized as the first genetic molecules."
>
> > Yes, by Leslie Orgel and others. �But that brings up the problem of a
> > "RNA/DNA takeover" to add to the already knotty problem of how the
> > "protein takeover" took place.
>
> If (as we discussed in an earlier thread), RNA/DNA was an advantageous
> carrier of genetic code information,

What's "iffy" about it? It's the part of biochemistry even laymen
know (or think they know).

> then there could have been a number
> of precursors: �PNA, polycyclic aromatic hydrocarbons (PAHs), perhaps
> others, all trying to survive and multiply and evolve. �And then a kind
> of "convergent evolution" took place, where all these different
> biochemical evolutionary paths all eventually ended up at the same
> place: RNA.

That's part of the "what", not the "how". If PNA was so successful,
how did it get supplanted so completely by RNA?

Even the later "protein takeover," when ribozymes got replaced by
protein enzymes, was not as complete as this; the ribosome is still
mostly RNA, and can do its job even without the huge number of
polypeptides bound in within it.

How did RNA even get started in the supplanting? Did PNA enzymes
start manufacturing RNA molecules within the protected confines of
protocells?

Keep in mind the following statement by Orgel and co-author:

Scientists interested in the origins of life seem to
divide neatly into two classes. The first, usually
but not always molecular biologists, believe that
RNA must have been the first replicating molecule
and that chemists are exaggerating the difficulty
of nucleotide synthesis. ... The second group
of scientists is much more pessimistic. They believe
that the de novo appearance of oligonucleotides on
the primitive earth would have been a near miracle.
(The authors subscribe to this latter view). Time
will tell which is correct.
--G. F. Joyce and Leslie E. Orgel, "Prospects
for understanding the origin of the RNA
world," in: _The RNA World_, ed. R. F.
Gesteland and J. F. Atkins, Cold Spring
Harbor Press, 1993, p. 19.

Here we are, almost two decades later, and there is no generally
acknowledged example of even one nucleotide (not to be confused with
base, i.e., purine or pyrimidine) being produced spontaneously in the
lab under simulated primitive earth conditions.

And even after they are produced, they need special conditions to keep
from deteriorating.

[Paul J Gans]

pnyikos <nyi...@bellsouth.net> wrote:

>On Nov 12, 7:02?pm, "Steven L." <sdlit...@earthlink.net> wrote:
>> On 11/12/2012 9:38 AM, pnyikos wrote:
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> > On Nov 11, 3:47 pm, Mike Painter <mddotpain...@sbcglobal.net> wrote:
>> >> " Scientists believe that prior to the advent of DNA as Earth's
>> >> primary genetic material, early forms of life used RNA to encode
>> >> genetic instructions. What sort of genetic molecules did life rely on
>> >> before RNA?
>> >> The answer may be AEG, a small molecule that when linked into chains
>> >> forms a hypothetical
>>

>> > Why hypothetical? ?Have they been unable to produce PNA from it?

>>
>> >> backbone for peptide nucleic acids, which have
>> >> been hypothesized as the first genetic molecules."
>>

>> > Yes, by Leslie Orgel and others. ?But that brings up the problem of a

>> > "RNA/DNA takeover" to add to the already knotty problem of how the
>> > "protein takeover" took place.
>>
>> If (as we discussed in an earlier thread), RNA/DNA was an advantageous
>> carrier of genetic code information,

>What's "iffy" about it? It's the part of biochemistry even laymen
>know (or think they know).

>> then there could have been a number

>> of precursors: ?PNA, polycyclic aromatic hydrocarbons (PAHs), perhaps
>> others, all trying to survive and multiply and evolve. ?And then a kind

As has been pointed out, we have no idea what "primative earth
conditions" were.

>And even after they are produced, they need special conditions to keep
>from deteriorating.

Why do you say that?

--
--- Paul J. Gans