So we have the deoxyribonucleocide triphosphates and we have that heat resistant DNA polymerase that are found in solution and which are swimming around this DNA molecule. And once we increase the temperature to 72 degrees Celsius, it's then that the DNA polymerase will bind onto the DNA and will begin adding those deoxyribonucleotide triphostate molecules and will begin to synthesize elongate that DNA. And so at the end of step number three, what we have formed is two identical copies of that DNA that we begin with. So after one cycle, we amplify the number to two. Now this is only one cycle of PCR if two cycles take place. So let's suppose this is cycle number one.