Final answer:
The termination stage occurs during translation when a ribosome reaches one of the three stop codons (UAA, UAG, or UGA), signaling the release of the new protein and the disassembly of the translation machinery.
Step-by-step explanation:
The stage of translation that occurs when a ribosome reaches a stop codon is called termination. This process takes place when the ribosome encounters one of the three stop codons - UAA, UAG, or UGA, which are recognized by release factors.
These codons do not specify an amino acid but instead signal the end of the protein synthesis process. As the stop codon aligns with the A site of the ribosome, a release factor binds, prompting the release of the newly synthesized polypeptide chain.
Consequently, the ribosomal subunits, along with the mRNA and tRNA, dissociate, allowing the components to be reused for translating another mRNA molecule.