What is the approximate temperature range for the extension phase in PCR?

The extension phase in the PCR (Polymerase Chain Reaction) is crucial for synthesizing new DNA strands. During this phase, DNA polymerase extends the primers by adding nucleotides complementary to the DNA template. The optimal temperature range for this process typically falls between approximately 68-75°C.

At these temperatures, DNA polymerase functions effectively, allowing it to catalyze the addition of nucleotides without denaturing the DNA template or the primers. This range is preferred because it is high enough to promote enzyme activity while still maintaining the structural integrity of the DNA.

In contrast, temperatures that are too high may hinder the polymerase's activity, while temperatures too low may lead to inefficient extension. Thus, the temperature range of 68-75°C specifically supports the efficient and accurate synthesis of the new DNA strands during the extension phase of PCR, making it the correct response.