Some amino acids are coded by more than one codon (known as degeneracy of codons), hence on deducing a nucleotide sequence from an amino acid sequence, multiple nucleotide sequence will be obtained.For e.g., Ile has three codons: AUU, AUC AUA hence dipeptide Met–Ile can have the following nucleotide sequence:
(i) AUG – AUU
(ii) AUG – AUC
(iii) AUG – AUA
and if, we deduce amino acid sequence the above nucleotide sequences all the three will code for Met–Ile