RNA World Comments

Here's some quotes from "The RNA World" from Strickberger's
textbook, Evolution and some comments by me:

1." because it is difficult to conceive how informational nucleotide sequences
could have evolved simultaneously with the polypeptide sequences necessary to
replicate them, researchers place emphasis on discoveries that some RNAs pssess
catalytic activity that might have enabled self replication."

Two comments  - IMO  nucleotide sequences were chosen for thermal stability in
a heat cycle that denatured strands completely in high heat and then annealed
variants in low. Each go round gave a selective advantage to certain sequences
- GC over AU over mistmatched bases. And the most stable sequence did not
completely denature but only partially. Thus it was selected over those that
completely denatured - etc. 
Also the most thermally stable fold from the sequence was selected. Look at
tRNA today - it is built to withstand denaturing.
The other comment is this - don't look for a SELF replicator. Look for a (more
likely) environmentally forced replicator (the heat that denatures the
nucleotide strands). This could have gone on for thousands of years thus giving
time for the SELF replicator to emerge.

2"...Joyce and Orgel suggest that the minimum length for RNA catalytic activity
is possibly "a triple stem-loop containing 40-60 nucleotides. Such an RNA
replicase could hardly have arisen by chance..."

But it could come from thermal selection over thousands of years.
This shifts the meaning of life as not that which feeds and breeds, (there must
have been some reason for chemicals to react to the environment through those
evolved strategies) but that which survives in a heat cycle by strategies that
include feeding and breeding.

3."As Moore puts it, "Why would a device for making polypeptides evolve in an
organism that had no use for protein?"

Moore is correct IMO. What we need to find is symbiosis between
amino acids and tRNA that in someway  would help the survival of both.

4."Ribas de Pouplana and coworkers show that an amino acid activating enzyme
used in protein synthesis was likely preceded during evolution by a transfer
RNA."

I agree and somewhere there's a symbiosis between tRNA and amino acids that
supports making peptide bonds out of the aa's, and perhaps helps tRNA by
keeping it from denaturing. I tend to think its some type of h-bond that
connects the two. And that it did this first at the acceptor stem of the tRNA.

Comment?
Tom Hendricks