RNA polymerase binds to the promoter region of DNA in the nucleus. It unwinds the DNA and reads the coding regions to create a complementary mRNA strand. The mRNA then passes through the nuclear pore into the cytoplasm. In the cytoplasm, the ribosome binds to the mRNA. Transfer RNA molecules bring amino acids to the ribosome based on the mRNA codons. The amino acids are linked together through peptide bonds to form a protein chain. Once a stop codon is reached, the ribosome releases the completed protein.