Genetic code

Codon usage table of Eschericia coli K12 DH10B. The first three characters are the codon, the second character in parentheses is the amino acid coded for by the codon, and the percentage is the relative usage of that codon in the genome across all CDSs.

The genetic code is the translation framwork of mRNA nucleotide sequence to protein amino acid sequence. mRNAs are read 5' to 3' using triplets of nucleotides. These triplets of nucleotides are called codons, and each codon codes for a single amino acid or a stop signal to end translation. While there are 64 possible codons (4x4x4), there are 20-21 amino acids and a stop signal. Thus, multiple codons can code for the same amino acids or stop signal, and the genetic code is redundant.