What is released into the cytosol when the stop codon is reached?

When the stop codon is reached during the process of translation, a critical event occurs that involves the termination of protein synthesis. The stop codon, which can be UAA, UAG, or UGA, signals to the ribosome that the polypeptide chain is complete.

Upon recognition of the stop codon, release factors bind to the ribosome, prompting it to release the completed polypeptide chain into the cytosol. This process effectively ends translation, and as a result, the mRNA is still present in the ribosome, but it is the completed polypeptide (the primary structure of the protein) that is released into the cytosol.

Therefore, while the mRNA itself is not released, the polypeptide is what ultimately enters the cytosol and begins the folding process necessary for the protein to achieve its functional structure. The mention of the mRNA in the context of being released into the cytosol is conceptually misleading; it remains within the ribosome until the entire ribosomal complex disassembles post-translation.

Thus, the option referring to mRNA may seem reasonable but does not accurately reflect what is specifically released into the cytosol upon reaching a stop codon in