Final answer:
Chain elongation during translation continues until a stop codon (UAA, UAG, or UGA) is encountered, leading to the release of the polypeptide chain and the dissociation of the ribosomal subunits.
Step-by-step explanation:
During translation, chain elongation continues until a stop codon is encountered. Translation elongation involves the ribosome moving along the mRNA, with new amino acids being added to the growing polypeptide chain. Each amino acid is brought to the ribosome by a tRNA and added to the chain through a process catalyzed by peptidyl transferase. This process repeats, with the ribosome proceeding one codon at a time and consuming ATP and GTP for energy.
Termination of translation occurs when the ribosome reaches a stop codon (UAA, UAG, or UGA), which does not code for any amino acid and does not have a corresponding tRNA. These stop codons are recognized by release factors that cause the polypeptide to be released from the ribosome. The ribosomal subunits then dissociate and are free to initiate another round of translation.