tRNA origin

This paper
Thermosynthesis as energy source for the RNA World:
A model for the bioenergetics of the origin of life
Anthonie W.J. Muller â??

Has a fascinating chart of the possible origin of tRNA.
I particularly found it interesting because I've long thought that
tRNA was the first RNA. Though I don't know enough to comment much on
his idea.
Here is the caption to the diagram

Fig. 6. The proposed evolution of tRNA and emergence of mRNA. (a) The
�rst tRNAs were minihelices that connected to amino acids and
yielded charged tRNAs. The charged tRNAs formed a protein with random
composition, a process catalyzed by an rRNA progenitor or possibly
a pF1 . (b) Using their arms positional tRNAs recognized a predecessor
and a follower, which resulted in a tRNA sequence that yielded a
small
protein sequence that was a key motif of pF1 . (c) The �rst tRNA of
the sequence extended to a template that bound all other motif tRNAs.
The positional tRNAs acquired anticodons that bound to codons on the
extension. (d) The extension was disconnected from the �rst tRNA
(arrow), and yielded a mRNA (start at 3â?² end). Mutual tRNA recognition
disappeared but tRNA:mRNA recognition remained: this transition
from mutually recognizing positional tRNAs to a set of regular mRNA-
codon recognizing tRNAs constituted the emergence of the genetic
code.
(e) Mutual tRNA recognition had disappeared. (f) A ribosome particle
containing rRNA emerged that performed (1) aminoacyl transfer from
tRNAs in the sequence given by mRNA to a growing peptide chain and (2)
translocation along mRNA in the 3â?² to 5â?² direction.

I don't know how much you can get without the diagram, but it is
fascinating.



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