Translation is the 2nd stage of protein synthesis, when the amino acids are assembled into a polypeptide. They are assembled into the sequence dictated by the sequence of codons on the mRNA (messenger RNA). The genetic code from DNA into mRNA, is now translated into a sequence of amino acids. This chain of amino acids is a polypeptide. It happens at ribosomes, which may be free in the cytoplasm but many are bound to the rough endoplasmic reticulum.