Q. 12.  There is only one possible sequence of amino acids when deduced from a given nucleotides. But multiple nucleotides sequence can be deduced from a single amino acid sequence. Explain this phenomenon.

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 obtaine, e.g., lle (Isoleucine) has three codons 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.