PCR (Polymerase Chain Reaction) is used in DNA sequencing primarily to amplify specific regions of DNA to generate millions or billions of copies of the target DNA sequence. This amplification is crucial when the original DNA sample is very small or limited, such as in forensic evidence or clinical samples. PCR produces enough copies of the target DNA to allow detailed study and sequencing, which is necessary because DNA sequencing techniques require a sufficient amount of DNA to analyze. PCR works by repeatedly heating and cooling DNA to denature it, allow primers to bind to target sequences, and enable DNA polymerase to synthesize new strands, resulting in exponential amplification of the target DNA fragment. This process ensures that even tiny amounts of DNA can be effectively studied and sequenced. Additionally, PCR allows for targeted sequencing where specific gene regions of interest can be selectively amplified and sequenced, aiding gene mutation detection, genetic research, disease diagnosis, and forensic analysis.