The salient features of genetic code are as follows:
1. The genetic codon is a triplet code and 61 codons code for amino acids and 3 codons do not code for any amino acid and function as stop codon (Termination).
2. The genetic code is universal. It means that all known living systems use nucleic acids and the same three base codons (triplet codon) direct the synthesis of protein from amino acids.
For example, the mRNA (UUU) codon codes for phenylalanine in all cells of all organisms. Some exceptions are reported in prokaryotic, mitochondrial and chloroplast genomes. However similarities are more common than differences.
3. A non-overlapping codon means that the same letter is not used for two different codons. For instance, the nucleotide sequence GUTJ and GUC represents only two codons.
4. It is comma less, which means that the message would be read directly from one end to the other i.e., no punctuation are needed between two codes.
5. A degenerate code means that more than one triplet codon could code for a specific amino acid.
For example, codons GUU, GUC, GUA and GUG code for valine.
6. Non-ambiguous code means that one codon will code for one amino acid.
7. The code is always read in a fixed direction i.e. from 5’ →3’ direction called polarity.
8. AUG has dual functions. It acts as a initiator codon and also codes for the amino acid methionine.
9. UAA, UAG (tyrosine) and UGA (tryptophan) codons are designated as termination (stop) codons and also are known as “non-sense” codons.
