In all 20 different amino acids can be used in the synthesis of proteins in the cells. There must be at least one specific codon for each amino acid. Thus, there has to be at least 20 different codons in the genetic code. There are only four bases- A, U, G and C (alphabets of the genetic code or m- RNA language) to be used in the formation of the codons. Now, suppose
- If each codon consists of only one base-
Then there can be only four codons possible: (4x1) = 4 codons.
(Not enough for the 20 different amino acids).
- If each codon consists of two bases-
Then maximum only 16 codons can be possible: (4x4) =16 codons.
(Not enough for the 20 different amino acids).
- If each codon consists of three bases-
Then maximum only 64 codons can be formed:
(4x4x4) =64 codons.
(More than enough for the 20 different amino acids)
Thus, each codon in the genetic code must be a triplet codon, i.e. it must consist of three nucleotide bases.
