92. (a): Codon are sequence of three nucleotides coding for the incorporation of one amino acid into a polypeptide chain. This code is almost universal in nature; identical sets of the three nucleotides are being used by viruses, bacteria and higher organisms. Since there are 64 possible combinations of the four different nucleotides in sets of three, there is a redundancy in the system, which means that most amino acids can be coded for by more than one triplet. Extremes are tryptophan (one codon: UGG) and leucine (six: codons). The genetic code is therefore said to be degenerate.