1) Reaction mixture that contains the DNA sample, free nucleotides, primers, and DNA polymerase.
2) The DNA mixture is heated to 95degrees Celsius to break the hydrogen bonds between the two strands of DNA.
3) the mixture is cooled to between 50 and 65 degrees Celsius so that the primers can bind to the strands. (ANNEALING).
4) the reaction mixture is heated to 72 degrees Celsius, so DNA polymerase can work and line up free DNA nucleotides along each template strand. Complementary base pairing occurs forming complementary strands.