tRNA evolution

As to why tRNA has the shape it has, there was a lot of theorizing about that in the 1970s from
Eigen's group and from a guy named Kuhn (I think). You definitely should become familiar with
Eigen's "hypercycle" theory if you are interested in this aspect of OOL.

As to what selective advantage tRNAs got from binding amino acids, and later discharging them, one
of the most interesting ideas is the "genomic tag" model of Weiner (Alan, I think) and Nancy
Maizels. They wrote a number of papers about it in the late 1980s and it also appears in editions of
Watson's textbook from that era. I think you will find their theory particularly interesting.

What are the best modern theories? I'm not sure, but you should be able to find them by doing a
citation search. The papers I mention will definitely be cited in newer theories.

Maybe someone with a better memory and/or library research tools can provide the exact citations.

<< More and more I think the major clue to the origin of life lies in tRNA. I was thinking last
night about how it could first start and came up with this scenario. We start with a single strand
of nucleotides. It has folds caused by the order of nucleotides, h-bonding and other forces. The
folds are bordered on both ends by unfolded stretches. Thus we have a folded portion with acceptor
like stems on both ends.

New stuff: Let's take this idea further. We have a folded nucleotide strand of RNA with two naked
ends - each with bases.

At some point I suggest that there are 3 bases on each end. There are at least 3 bases because that
allows for one MIDDLE base. And a protected 2nd position middle base is essential.

Here's a possibility for those 3 and in both cases we are listing them in this direction - from the
folded strand out toward the naked out-on-a-limb end.

I suggest at both ends we have these 3 bases: G/N/Wobble - Where G is always the first base Where N
= A,U,C, or G as possibilities for the 2nd base Where there is wobble in the third base. because it
is the most exposed.

We have now the possibility of 4 codons that happen to code for the four most produced amino acids
in most prebiotic experiments:

(G N Wobble)

G G wobble = Glycine G C wobble = Alanine G A wobble = Aspartic Acid G U wobble = Valine

Now note that glycine and alanine are some what neutral in not being either hydrophobic or philic,
but that Aspartic acid is philic, and Valine is phobic.

And in similar conditions of heat/wet and dry/pH; I would think both ends would be selected when
their codons matched. And when they did not match they would not be selected. Also when both end's
codons matched , the number of h-bonds would match too. Thus both would be denatured at the same
time - thus they would both release their h-bonds at both ends at the same time. etc. That would be
selected for.

IF any of this has a basis in fact, then they suggest two immediate questions:
1. why would G be favored in first position or in the position next to the RNA folded portion.
2. how would these codon ends connect to AA's - what part of the AA's would they connect to - and
how would tt help in a prebiotic chemical symbiosis between the RNA and the AA's?

Comment? Tom Hendricks

<< You definitely should become familiar with Eigen's "hypercycle" theory if you are interested in
this aspect of OOL.

Yes but that's not quite what I'm suggesting.

As to what selective advantage tRNAs got from binding amino acids, and later discharging them, one
of the most interesting ideas is the "genomic tag" model of Weiner (Alan, I think) and Nancy
Maizels. They wrote a number of papers about it in the late 1980s and it also appears in editions of
Watson's textbook from that era. I think you will find their theory particularly interesting.

TH I've seen them mentioned - but there's nothing on the net or in old textbooks I've go Z**t. Does
any reader know what was the jist of their ideas.

What are the best modern theories? I'm not sure, but you should be able to find them by doing a
citation search. The papers I mention will definitely be cited in newer theories.

TH I don't think any of the modern hypothesis are correct. If they aren't based on life as a
reaction to a heat cycle, I don't think they can be correct. That's why I'm looking still.

Maybe someone with a better memory and/or library research tools can provide the exact citations.