During the polymerase chain reaction, the two DNA strands are separated at 95°C, after which the reaction mixture is cooled to 54°C to allow the primers to hybridize to the DNA strands. Why do primer‑template hybrids form instead of parent DNA duplexes?

Answer and Explanation:

When the reaction mixture is cooled to 54ºC, the primer-template hybrids form preferentially instead of parent DNA duplexes because primers are added in excess with respect to the amount of DNA to amplificate. Thus, there are more probabilities of primer-template duplexes formation.