What crucial step follows denaturation in the PCR process?

In the PCR (Polymerase Chain Reaction) process, the step that follows denaturation is the annealing of primers. During denaturation, the double-stranded DNA is heated to separate it into two single strands. Once this separation occurs, the reaction temperature is lowered to allow primers, which are short single-stranded sequences of nucleotides, to bind or "anneal" to their complementary sequences on the single-stranded DNA templates. This is a critical step because the primers are necessary for the DNA polymerase enzyme to initiate DNA synthesis during the subsequent elongation phase.

The temperature during the annealing step is optimized to ensure that the primers can bind specifically and effectively, minimizing non-specific binding and improving the efficiency of the subsequent amplification. Without properly annealed primers, the DNA polymerase would not have a starting point for synthesis, making this step essential for successful PCR.