polypeptide chain termination
The termination of protein synthesis occurs when a stop translation codon (UAA, UAG, UGA) is in the A site of the ribosome. There are usually no tRNAs that have anticodons complementary to the three stop translation codons. Instead a chain termination factor (protein) occupies the ribosomal A site.
The C terminal amino acid is then cleaved from the transfer RNA and the completed polypeptide chain is released from the ribosome complex.
A cartoon animation of the process of polypeptide chain temination can be seen by clicking here