Question

Explain briefly the Polymerase Chain Reaction (PCR).

Hint:

PCR requires primers, DNA polymerase, nucleotides, and a thermal cycler.

Answer 1

The Polymerase Chain Reaction (PCR) is a molecular biology technique used to amplify (make many copies of) a specific DNA sequence in vitro. It was developed by Kary Mullis in 1983. Steps of PCR: \begin{enumerate} \item Denaturation: Double-stranded DNA is heated to about 94–96°C to separate into two single strands. \item Annealing: The reaction is cooled to 50–65°C so that primers bind (anneal) to the complementary sequences on the DNA strands. \item Extension: DNA polymerase (commonly Taq polymerase) extends the primers at about 72°C, synthesizing new DNA strands. \end{enumerate} These steps are repeated in cycles (usually 25–35 cycles), leading to exponential amplification of DNA. Applications: Used in disease diagnosis, forensic science, paternity testing, and genetic research. Final Answer: PCR is a method to amplify DNA sequences using repeated denaturation, annealing, and extension steps.