Transfer RNA (tRNA) is the central intellectual property in the evolution of life on Earth. tRNA evolved from repeats and inverted repeats of known sequence. The anticodon and the T stem-loop-stems are homologs with significant conserved sequence identity. A number of models have been advanced to explain tRNA evolution. No 2-minihelix model or accretion model (built a stem at a time) can be correct, in part because of anticodon and T stem-loop-stem identity. Only a 3-minihelix model is adequate.
Keywords: 2-minihelix model; 3-minihelix model; Accretion model; tRNA evolution.