In my origin scenario I suggested that a single RNA strand folded upon itself with two ends loose. This was one of the first and earliest key developments in the origin. Now I think a more reasonable scenario for this early period, is short complimentary strands base paired together with 4 ends sticking out. This lets each end have a loose 3' end that is stacked but not base paired. Its on these two ends that I think other prebiotic material h-bonded to. And remember though h-bonds are slight there is no reason to think that these 'loose ends' are limited to h-bonding to just one aa, or one other rna. They could be quite long and have many h-bond partners. Enough so that for every 3 (allowing a protected middle spot) there could be h-bonding to either an aa or other rna. (Later this would lead to the tRNA system with aa at one end and mRNA at the other) This set the stage for the adaptor molecule to connect up the two worlds of aa's and rna's. The h- bonding is possible between aa and proto-tRNA yet is very weak. But because it is possible it probably happened, and would be hard to stop from happening. This building on the loose 3' ends of a paired proto RNA was thermally stable and helped all survive in a type of chemical symbiosis. Notes: Whether this means anything or not, I find it strange that in the anticodon loop, there is a 2nd loop cleaved. It has this coding uuu - ACCA (as in the acceptor stem) -cuacg - aaa. Base 76 is not stacked. That leaves a 3 base stacked but unpaired row of 73 (discriminator base) 74, 75. I wonder if these 3 didn't once act as the codon does or vice versa. I think the anticodon loop was first a loose end that later evolved to a closed loop. The process of making a tRNA seems to suggest that possibility. Thus it looks like that on earliest times, we had an RNA molecule with two 3' loose ends. Note in both ends there is the 3rd base in least stacked or naked end territory. That would seem to suggest wobble in that position. Also note how important shape is for the 3rd wobble position. it seems that for every codon either pyrimidine can code and is interchangeable in 3rd and almost in every case, either purine can code in 3rd. Comment? Tom Hendricks The main points of my hypothesis are: 1. How life began as a reaction to the sun/UV and the thermal cycle of hot-dry-sun/cold-wet-night. Then continued as an energy moderator with modification through descent. 2. The Four Options and how they relate to thermodynamics, biological classification, the first cell, modification on all levels, psychological behavior of individuals and groups, inner conflicts and a therapy of resolving them, etc. 3. Model showing relationship between adaptation fitness and natural selection. How it supports punctuated equilibrium and the 'slope and plateau' model etc. For a reader friendly summary see my arts/media website url for Musea issue#122 http://musea.digitalchainsaw.com/122Musea1.html Tom Hendricks, Hendricks Health Theory text files at <A HREF="http://www.ediacara.org/~josh/hendricks.html">http://www.ediacara.or g/~josh/hendricks.html (text #10 has a not-too-out of date summary) Remember YOUR chemistry can't hide from MY sun.