During which phase of PCR do primers bind to the DNA template?

The phase of PCR where primers bind to the DNA template is known as the annealing phase. During this step, the temperature of the reaction is lowered after the initial denaturation phase, which separates the double-stranded DNA into single strands. At this lower temperature, the primers can bind (or anneal) to their complementary sequences on the single-stranded DNA.

This binding is essential for the subsequent amplification of the target DNA region, as the primers provide a starting point for the DNA polymerase enzyme to begin synthesizing new DNA strands during the next phase, which is extension. If the primers do not anneal effectively to the target sequences, the PCR process will not amplify the desired DNA region, making this phase critical for the overall success of the PCR.

The other phases, such as denaturation and extension, serve different purposes: denaturation separates the DNA strands, and extension involves the synthesis of new DNA strands from the bound primers. Quantification is not a standard phase in the classical PCR process; rather, it's a term that might relate to the analysis of PCR products in real-time PCR or quantitative PCR contexts.