codon AUGSTART codons The codon AUG is called the START codon as it the first codon in the transcribed mRNA that undergoes translation. AUG is the most common START codon and it codes for the amino acid methionine (Met) in eukaryotes and formyl methionine (fMet) in prokaryotes.
AUGThe start codon in all mRNA molecules has the sequence AUG and codes for methionine.
In eubacteria, codons such as GUG and UUG, which are related to AUG by a single base change, are occasionally used for initiation. However, these codons are read by the same initiator tRNA and are, therefore, translated as formylmethionine. In eukaryotic systems, AUG is almost exclusively the codon used for initiation.
Hence, AUG is the initiation codon.
The rational design of theoretical minimal RNA rings predetermines AUG as the universal start codon. This design maximizes coded amino acid diversity over minimal sequence length, defining in silico theoretical minimal RNA rings, candidate ancestral genes.
A start codon is made up of the letters ATG, which codes for the amino acid methionine. When the machinery of the cells sees that first ATG, it knows to start making the protein there.
Each three-letter sequence of mRNA nucleotides corresponds to a specific amino acid, or to a stop codon. UGA, UAA, and UAG are stop codons. AUG is the codon for methionine, and is also the start codon.