Translation concludes when a stop codon is encountered on the mRNA molecule.

Translation is the biological process through which the genetic information encoded in mRNA is utilized to synthesize proteins. This crucial process takes place in the ribosome, which interprets the mRNA sequence and employs it as a template to assemble a chain of amino acids. The ribosome reads the mRNA in triplets of nucleotides known as codons, matching each codon with its corresponding amino acid.

There are a total of $64$ possible codons, yet only $20$ distinct amino acids are used in protein synthesis. This results in several amino acids being encoded by more than one codon. Additionally, there are three specific codons that do not correspond to any amino acid; instead, they signal the termination of the protein synthesis process. These are referred to as stop codons, specifically UAA, UAG, and UGA.

Upon reaching a stop codon on the mRNA molecule, the ribosome recognizes this as a signal to halt translation. Consequently, the newly synthesized protein is released from the ribosome and begins to fold into its final three-dimensional structure. Simultaneously, the mRNA molecule is also released and can be reused for the synthesis of another protein.

In summary, translation termination occurs when a stop codon is reached on the mRNA molecule. This event signals the ribosome to release both the newly synthesized protein and the mRNA, allowing the protein to properly fold into its final structure.