Final answer:
The ribosome moves down one codon during the translation process in protein synthesis through translocation, which is powered by GTP hydrolysis and the action of EF-G. This step is crucial for the ribosome to read mRNA and synthesize proteins accordingly.
Step-by-step explanation:
What stimulates the ribosome to move down one codon is a process called translocation, which is an essential part of the translation phase of protein synthesis. During translocation, the ribosome moves along the mRNA molecule towards the 3' end by a distance of one codon (three nucleotide bases). This movement is facilitated by the hydrolysis of Guanosine triphosphate (GTP) and requires the action of elongation factor-G (EF-G), also known as translocase. As a result of this, the tRNA that was in the A site moves to the P site, carrying the growing polypeptide chain, and the deacylated tRNA in the P site moves to the E site and is then released into the cytosol.
At the end of the translation process, when a stop codon is reached, release factors will bind, causing the polypeptide to be released and the ribosomal subunits to disassociate. The ribosome can then be reassembled for another round of protein synthesis.