acid chain (protein) goes into the lumen (inner chamber) of the ER for packaging, sorting, etc.The actual formation of the polypeptide chain occurs only with the assistance of tRNA which brings single amino acids to the mRNA, beginning with methionine (coded AUG). The first tRNA binds at the P-site, but when the A site is occupied by the subsequent tRNA molecule, the original amino acid moves over to the second tRNA. Then the first tRNA molecule leaves and the second moves over to take its place at the P-site. This process continues until each of the codons (series of three nucleotides located on the mRNA each coding for a single amino acid) on the mRNA has been decoded and formed a specific amino acid on the polypeptide chain. When the termination sequence is reached, the chain is finally released.At this point, the outcome of the new protein is left to be determined by the other organelles in the cell. The DNA and RNA have served their purposes. ...
