In eukaryotes, mRNA and tRNA, as well as the ribosomal subunits made using rRNA, must be exported out of the nucleus through the nuclear pore complexes.
Translation: Initiation
The mRNA molecule to be decoded binds to one subunit of the ribosome, then the other ribosomal subunit binds to both of those. In the process, a tRNA with the amino acid methionine attached docks in the ribosome's P site.
Translation: Elongation
The following cycle is repeated again and again, elongating the polypeptide by 1 amino acid per cycle.
(1) a charged tRNA docks in the A site and the existing, growing polypeptide is transferred from the tRNA molecule in the P site to the new tRNA's amino acid.
(2) translocation: The ribosome moves 3 bases along the mRNA, moving the uncharged tRNA in the P site into the E (exit) site, the tRNA in the A site (with the polypeptide now attached) into the P site, and positioning a new codon into association with the now-empty A site.
(3) Back to step (1)
Translation: Termination
Eventually, translocation brings a stop codon into the position associated with the empty A site. A stop codon does not code for an amino acid, but for a release factor. The release factor binds and then frees the polypeptide and dissociates the ribosome.