  A hypothesis of the evolution of the genetic code is proposed, the leading
mechanism of which is the nucleotide spontaneous damage leading to
AT-enrichment of the genome. The hypothesis accounts for stability of the
genetic code towards point mutations, the presence of code dialects, emergence
of stop codons, emergence of the DNA double helix and the symmetry of the
genetic code table. The assumption of the originally triplet structure of the
genetic code has been substantiated. A hypothesis concerning the primary
structure of the first gene and the first protein has been proposed.
