How the DNA directs Protein Synthesis 1. When a cell needs more of a protein, a section of the DNA unzips at a specific gene. (A gene is a section of DNA that codes for a specific protein.) 2. Messenger RNA (mRNA) nucleotides get in sequence based on the order of one of the DNA strands. 3. The mRNA leaves the nucleus and moves to the ribosome in the cytoplasm. 4. The ribosome “reads” the mRNA nucleotides in groups of three called codons. 5. Specific transfer RNA (tRNA) molecules bring specific amino acid molecules to the ribosome. 6. The anti-codons (groups of three nucleotides on the tRNA) attach to codons that they match. 7. The amino acids attach together to make a polypeptide (protein). 8. The polypeptide folds into a 3-dimensional structure the body can use.