Firmitas

Universal Codon of Life

Revision 7
© 2006 by Zack Smith. All rights reserved.

The Codons

All genes are composed of sequences of codons, which are triplets of nucleotide bases (A C G T/U). Ribosomes convert these sequences into proteins, which are polymers of amino acids.

Of the 64 possible codons, there are 20 amino acids coded for, 3 stop codons, and 1 start codon (the amino acid methionine). There are many redundant codons, which is important for protecting against transcription errors and mutations.

The Universal Codon of Life

First Base Second Base Third Base
U C A G
U UUU = phenylalanine UCU = serine UAU = tyrosine UGU = cysteine U
UUC = phenylalanine UCC = serine UAC = tyrosine UGC = cysteine C
UUA = leucine UCA = serine UAA = stop UGA = stop A
UUG = leucine UCG = serine UAG = stop UGG = tryptophan G
C CUU = leucine CCU = proline CAU = histidine CGU = arginine U
CUC = leucine CCC = proline CAC = histidine CGC = arginine C
CUA = leucine CCA = proline CAA = glutamine CGA = arginine A
CUG = leucine CCG = proline CAG = glutamine CGG = arginine G
A AUU = isoleucine ACU = threonine AAU = asparagine AGU = serine U
AUC = isoleucine ACC = threonine AAC = asparagine AGC = serine C
AUA = isoleucine ACA = threonine AAA = lysine AGA = arginine A
AUG = methionine ACG = threonine AAG = lysine AGG = arginine G
G GUU = valine GCU = alanine GAU = aspartate GGU = glycine U
GUC = valine GCC = alanine GAC = aspartate GGC = glycine C
GUA = valine GCA = alanine GAA = glutamate GGA = glycine A
GUG = valine GCG = alanine GAG = glutamate GGG = glycine G

Start & Stop codons

There is only one start codon, which is AUG. This is also the methionine amino acid.

There are three stop codons: UAA, UGA, UAG.