Final answer:
The termination phase of translation occurs when a stop codon (UAA, UAG, or UGA) is encountered by the ribosome, leading to the release of the new protein and the dissociation of the ribosomal components.
Step-by-step explanation:
The stage of translation that occurs when a ribosome reaches a stop codon is called termination. Termination is a crucial phase in the process of protein synthesis. During this stage, the ribosome recognizes one of the three stop codons (UAA, UAG, or UGA) in the mRNA. A release factor then binds in the A site of the ribosome, prompting the newly synthesized polypeptide chain to be released. Furthermore, the ribosomal subunits, along with the mRNA and tRNAs, dissociate from each other. The ribosomal subunits are then free to participate in another round of translation, whereas the mRNA is eventually degraded and its nucleotides recycled.