Video Transcript
AUG is a start codon. Which of the following best explains what this means? (A) AUG is recognized as the site where the large ribosomal subunit should join. (B) AUG determines where the polypeptide chain formed will bind to another chain. (C) AUG is recognized as the point where translation should begin. Or (D) AUG codes for the first alphabetical amino acid, alanine.
This question requires us to explain what a start codon does. So let’s review the function of start codons in translation. As the question notes, the sequence for the start codon is AUG. Unlike stop codons that have three different possible sequences, the start codon only has one, which codes for the amino acid methionine. This start codon signals the ribosome to begin the process of translation. You might remember that translation occurs when an mRNA sequence is read by a ribosome. Every three mRNA nucleotides, called a codon, is recognized by a complementary tRNA molecule, which brings along the corresponding amino acid.
Translation continues with the ribosome moving along the mRNA and matching subsequent codons with amino acids that are joined to form a polypeptide chain. While a start codon initiates translation, translation ends when a stop codon is reached. So in response to “Which of the following best explains the function of a start codon?” the correct answer is (C). AUG is recognized as the point where translation should begin.
