Molecular Basis of Inheritance — BIOLOGY STD 12 Science — Question

Since there are only four bases which code for twenty amino acids, the code should be made up of three bases, i.e., (4 × 4 × 4) = 64 codons; a number more than the required. If the codon consists of four letters, only (4 × 4), only sixteen codons are possible, which is less than the required. Hence the codon is a triplet. As the ribosome moves on mRNA, continuously without break, the codons are read in a contiguous manner.