During which stage of PCR do primers bond to the template DNA?

The process of PCR, or Polymerase Chain Reaction, involves several distinct stages, each critical to amplifying DNA. During the annealing stage, primers—short sequences of nucleotides complementary to the target DNA segment—bind to the template DNA. This bonding is facilitated by lowering the temperature after the initial denaturation phase, allowing the double-stranded DNA to separate into two single strands.

During annealing, the temperature is optimal for the primers to attach to their complementary sequences on the template strands, effectively marking the starting points for DNA synthesis. This step is crucial because the primers provide the necessary starting points for DNA polymerase to begin replication in the next stage. If the temperature is not carefully controlled during this phase, the primers may not bind correctly, which can lead to inefficient or failed amplification of the target DNA.

Understanding the role of the annealing stage is essential in mastering PCR techniques, as it directly influences the specificity and efficiency of the amplification process.