Characteristics of Genetic Code :

1. Triplet Code : Three adjacent nitrogen bases constitute a codon which specifies the placement of one amino acid in a polypeptide. 

2. Start Signal: Polypeptide synthesis is signalled by two initiation codons – methionine AUG or codon and GUG or valine codon. 

3. Stop Signal: Polypeptide chain termination is signalled by three termination codons – UAA (ochre), UAG (amber) and UGA (opal). They do not specify any amino acid and are hence also called nonsense codons. 

4. Universal Code : The genetic code is applicable universally, i.e., a codon specifies the same amino acid from a virus to a tree or human being. Thus, /wRNA from chick oviduct introduced in Escherichia coli produces ovalbumin in the bacterium exactly similar to one formed in chick. 

5. Nonambiguous Codons : One codon specifies only one amino acid and not any other. 

6. Related Codons : Amino acids with similar properties have related codons, e.g., aromatic amino acids tryptophan (UGG), phenylalanine (UUC, UUU), tyrosine (UAC, UAU). (Any four points)