The AUG codon has a dual function. It serves as the codon and it encodes the amino acid .

The AUG codon has a dual function. It serves as the start codon for translation initiation and it encodes the amino acid methionine.

1. Start Codon: The AUG codon is critical because it marks the beginning of the protein synthesis process. Ribosomes recognize this codon as the point at which translation should begin, ensuring that the genetic code is read in the correct frame.

2. Amino Acid Encoding: AUG is unique because it encodes the amino acid methionine, which is the first amino acid in most newly synthesized polypeptides during translation. Even though methionine can be present in other positions within proteins, its role as an initiator is paramount.

This dual functionality of AUG is crucial in biological processes, allowing efficient protein synthesis while ensuring that the polypeptides are synthesized starting from the correct point in the mRNA. In summary, AUG is key for the initiation of protein synthesis as well as encoding an essential amino acid.