In a typical PCR reaction, describe what is happening in stages occurring at temperature ranges (a) 92-26 °C, (b) 45-65 °C, and (c) 65-75 °C.

Key Concepts

Polymerase Chain Reaction (PCR)

PCR is a molecular biology technique used to amplify specific DNA sequences. It involves repeated cycles of denaturation, annealing, and extension, allowing for the exponential increase of the target DNA. Understanding PCR is essential for grasping how temperature changes affect the reaction stages.

Denaturation

Denaturation is the first step in PCR, occurring at high temperatures (around 92-96 °C). During this stage, the double-stranded DNA melts open to form two single strands, breaking the hydrogen bonds between the base pairs. This step is crucial for making the DNA accessible for the subsequent annealing process.

Annealing and Extension

Annealing occurs at lower temperatures (45-65 °C), where primers bind to the single-stranded DNA templates. This is followed by the extension phase (65-75 °C), where DNA polymerase synthesizes new DNA strands by adding nucleotides to the primers. These stages are vital for the specificity and efficiency of DNA amplification in PCR.