A sequence of mRNA is use to generate a protein (translation). mRNA binds to a ribosome, the machinery that organises the protein sequence production. The large ribosomal subunit has two binding sites for transfer RNA (tRNA). Each tRNA carries an amino acid which will be incorporated into the newly forming protein polypeptide. After the first tRNA has bound to the ribosome, its amino acid is passed on the second tRNA amino acid. In this way the protein sequence is built up. Once the sequence is complete, the amino acid sequence detaches from the ribosome and folds into its protein shape.