In translation, the start codon AUG codes for which amino acid in the growing polypeptide chain?

In translation, the start codon AUG codes for which amino acid in the growing polypeptide chain?

• A. Lysine
• B. Methionine
• C. Valine
• D. Alanine

Answer: (B)

The start codon AUG specifies methionine as the first amino acid in the growing polypeptide. During initiation, the initiator tRNA carrying methionine binds to this codon at the P site of the ribosome, setting the reading frame for the rest of the protein. In bacteria, this methionine is often formylated (formylmethionine) at initiation, but the codon still corresponds to methionine. As elongation proceeds, other codons recruit different amino acids. Sometimes the initial methionine is removed after translation, but the codon itself codes for methionine.

The start codon AUG specifies methionine as the first amino acid in the growing polypeptide. During initiation, the initiator tRNA carrying methionine binds to this codon at the P site of the ribosome, setting the reading frame for the rest of the protein. In bacteria, this methionine is often formylated (formylmethionine) at initiation, but the codon still corresponds to methionine. As elongation proceeds, other codons recruit different amino acids. Sometimes the initial methionine is removed after translation, but the codon itself codes for methionine.