This Polymerase Chain Reaction process demonstrates the use of short DNA sequences known as primers to choose the portion of the genome to be amplified. The sample temperature is raised and lowered repeatedly to aid a DNA replication enzyme in copying the target DNA sequence. This Polymerase Chain Reaction process also demonstrates the three-step process repeated in cycles. The initial step is the denaturation or the separation of the two strands of the DNA molecule. PCR is based on three simple steps that are required for any DNA synthesis reaction: denaturation of the template into single strands; annealing of primers to each original strand for new strand synthesis; and extension of the primer-derived new DNA strands.