Final answer:
During translocation in protein synthesis, the ribosome moves one codon along the mRNA, shifting the nascent polypeptide from the A site to the P site, and the empty tRNA exits through the E site. This process elongates the polypeptide chain as the ribosome progresses.
Step-by-step explanation:
During translocation, an event in the elongation stage of protein synthesis, the ribosome moves along the mRNA in the 5' direction by a distance of one codon, which is three bases. This movement is facilitated by a GTP-dependent protein known as elongation factor-G or translocase. As a result of translocation, the dipeptide that was in the A site of the ribosome is shifted to the P site along with its tRNA, and the deacylated tRNA leaves the ribosome from the E site, making space for a new aminoacyl-tRNA to enter the A site. This process contributes to the creation of the polypeptide chain by moving the ribosome to the next codon of the mRNA.