Final answer:
The three steps of a PCR cycle are denaturation, annealing, and extension. Denaturation separates the DNA strands, annealing allows the primers to bind, and extension synthesizes new DNA strands.
Step-by-step explanation:
Denaturation: The first step of a PCR cycle is denaturation, where the temperature is increased to 94-96°C to separate the double-stranded template DNA strands.
Annealing: The second step is annealing, where the temperature is lowered to about 68°C to allow the primers to bind to their complementary locations on the single-stranded templates.
Extension: The third step is extension, where the temperature is increased to about 72°C for Taq polymerase to synthesize new DNA strands by extending from the primers.