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