Identify the correct sequence of steps in each cycle of Polymerase Chain Reaction :

The Polymerase Chain Reaction (PCR) amplifies a specific DNA segment through repeated thermal cycles. Each cycle consists of three distinct steps performed in a fixed order.

1. Denaturation: The reaction mixture is heated to around 94‑98 °C. This high temperature breaks the hydrogen bonds between the two strands of the DNA template, resulting in single‑stranded DNA that can serve as a template for synthesis.

2. Annealing: The temperature is lowered to about 50‑65 °C, allowing short DNA primers to bind (anneal) to their complementary sequences on the single‑stranded template. The primers define the start and end points of the region to be amplified.

3. Extension (or Elongation): The temperature is raised to the optimal working temperature of the DNA polymerase (typically ~72 °C for Taq polymerase). The polymerase extends each primer by adding nucleotides, synthesizing a new DNA strand complementary to the template.

This three‑step sequence—Denaturation → Annealing → Extension—is repeated 25‑35 times, exponentially increasing the amount of the target DNA fragment.