Figure 9

Origin of the translation system and the genetic code in the RNA World. Step 5: Small amino-acid-binding RNAs (T RNAs) evolve via selection for accumulation of amino acids. Once species of the T RNAs evolves the capacity of autocatalytic aminoacylation, further enhancing amino acid accumulation, The actual substrate, probably, was an activated amino acid derivative, such as an aminoacyl adenylate.