Three cycles of the Polymerase Chain Reaction (PCR) are shown. During each cycle, DNA molecules are denatured, annealed to specific oligonucleotide primers, and the primers extended with a thermostable DNA polymerase. Note the exponential nature of the amplification process (for example: thirty cycles would amplify DNA by a factor of 230= 1,073,741,824 or 1 billion times). The "Final Amplified Molecule" shows the product after many PCR cycles. See page 922, Figure 24A.1 for comparison.