The universally valid genetic code is the final result of a multi-stage course of development. Degeneracy, as an important property of the genetic code, was possibly not yet present in the earliest code, first appearing at a later stage of development. Possibly this step in development is coupled with the presence of a total of four amino acid groups. Each group contains a specific number of amino acid. Amino acid groups: — hydrophobic– - weakly hydrophobic or polar but uncharged – (...) - hydrophilic, acidic – - hydrophilic, basic – - hydrophobic, aromatic In a subsequent stage of development the number of amino acids increases further. At the same time the code becomes more degenerate. The universal genetic code is characterized by three constants of being degenerate. Its immediate predecessor has linear degeneration with two constants. The mitochondrial code represents a transitional form between these two codes. (shrink)