Evolution of the genetic code. Why are there strong and weak letter doublets? The first gene, the first protein. Early (ancient) biosynthesis of protein

of the genetic code. Why are there strong and weak letter doublets? The first gene, the first protein. Early (ancient) biosynthesis of protein. The idea of the evolution of the genetic code from the CG to the CGUA alphabet has been developed further. The assumption of the originally triplet structure of the genetic code has been substantiated. The hypothesis of the emergence of stop codons at the early stage of the evolution of the genetic code has been additionally supported. The existence of strong and weak letter doublets of codons and the symmetry of strong doublets in the genetic code table, discovered by Rumer, have been explained. A hypothesis concerning the primary structure of the first gene and the first protein has been proposed. Strong and weak letter doublets. Rumer's symmetry. Rumer proposed this representation of the table of letter doublets for the genetic code in order to illustrate the symmetry he had discovered [1,2] (see Table 1). A Thr Ser Ile Asn Arg Met Lys Table 1. The symmetry of the table of the letter doublets for the genetic code (according to Rumer). Strong letter doublets are marked in gray. A nucleotide triplet can be assumed to change its form, but in this case a change in the form of the first two nucleotides occurs due to the third. Here I do not speak of the form of the triplet in the