The Process of Translation Translation begins with the binding of the mRNA chain to the ribosome. The first codon, which is always the start codon methionine, fills the P site and the second codon fills the A site. The tRNA molecule whose anticodon is complementary to the mRNA forms a temporary base pair with the mRNA in the A site. A peptide bond is formed between the amino acid attached to the tRNA in the A site and the methionine in the P site. The ribosome now slides down the mRNA, so that the tRNA in the A site moves over to the P site, and a new codon fills the A site. (one way to remember this is that the A site brings new amino acids to the growing polypeptide at the P site) The appropriate tRNA carrying the appropriate amino acid pairs bases with this new codon in the A site. A peptide bond is formed between the two adjacent amino acids held by tRNA molecules, forming the first two links of a chain. The ribosome slides again. The tRNA that was in the P site is let go into the cytoplasm, where it will eventually bind with another amino acid. Another tRNA comes to bind with the new codon in the A site, and a peptide bond is formed between the new amino acid to the growing peptide chain. The process continues until one of the three stop codons enters the A site. At that point, the protein chain connected to the tRNA in the P site is released. Translation is complete.