(i) Triplet in Nature :–
A codon is composed of three adjacent nitrogen bases which specifies one amino acid in polypeptide chain.
For Ex. : . In m–RNA if there are total 90 N2 – bases. . Then this m–RNA determines 30 amino acids in polypeptide chain. .
(ii) Universality :–
The genetic code is applicable universally. The same genetic code is present in all kinds of living organism including viruses, bacteria, unicellular and multicellular organisms.
(iii) Non – Overlapping :–
A nitrogen base is a constituent of only one codon.
(iv) Comma less :–
There is no punctuation (comma) between the adjacent codon i.e. each codon is immediately followed by the next codon.
(v) Degeneracy of Code
Some amino acids are coded by more than one codon, hence the code is degenerate.
There are 64 codons for 20 types of amino acids, so most of the amino acids (except two) can be coded by more than one codon. Single amino acid coded by more than one codon is called ‘‘Degeneracy of genetic code’’.
(vi) Start Signal
AUG has dual functions. It codes for Methionine (met) , and it also act as initiator codon. Also sometime GUG or valine codon also initiate the chain and has dual function.
Source of Picture : NCERT