In PCR, which phase follows annealing?

In PCR, the phase that follows annealing is extension. During the extension phase, DNA polymerase synthesizes new strands of DNA by adding nucleotides to the annealed primers, effectively elongating the DNA strands.

This process occurs at a temperature optimal for the activity of the DNA polymerase, usually around 72°C for Taq polymerase. At this temperature, the polymerase can efficiently incorporate complementary nucleotides to the template DNA strand. The extension phase allows for the amplification of the target DNA sequence, which is the primary goal of the PCR process.

Understanding the sequence of these steps is essential in molecular biology for troubleshooting PCR reactions and for designing experiments. The annealing phase prepares the primers to bind to the DNA template, and following that, the extension phase is critical for the actual replication of DNA, ultimately leading to the exponential amplification of the target sequence.