What is the second step of the Polymerase Chain Reaction (PCR)?

The second step of the Polymerase Chain Reaction (PCR) is annealing. During this phase, the temperature is lowered to allow the primers to bind or hybridize to their complementary sequences on the template DNA strands. This is crucial for the PCR process because the primers serve as the starting point for DNA synthesis, guiding the DNA polymerase to the right location for replication.

The annealing temperature must be optimized to ensure specific binding of the primers to the target DNA sequence, minimizing the risk of non-specific binding. This step directly follows the denaturation step, where the double-stranded DNA is heated to separate it into two single strands. After annealing, the process continues with the extension step, where DNA polymerase synthesizes new DNA strands. The precision of the annealing step is key to the overall success of PCR, as it ensures that the amplification is targeted effectively.