Why is an amino acid encoded not by one or two, but by three consecutive nucleotides?

The composition of DNA and RNA includes four types of nucleotides. At the same time, 20 protein-forming amino acids must be encoded. If only one nucleotide was responsible for one amino acid, then only 4 amino acids could be encoded. Nucleotide doublets (two) would be enough only for 42 = 16 amino acids. It is easy to calculate that the number of possible combinations of the four types of three nucleotides is 43 = 64. This is more than enough to encode the 20 amino acids that make up the proteins.

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