What technique is commonly used to extract DNA from a sample?

The Polymerase Chain Reaction (PCR) is a widely used technique for extracting DNA from a sample. This method allows for the amplification of specific DNA sequences, making it possible to generate millions of copies of a particular DNA fragment from a small initial sample.

PCR is essential in forensic science because it enables investigators to analyze trace amounts of DNA, which could be present in crime scene samples. The process involves a series of temperature changes that facilitate the denaturation of DNA, annealing of primers, and extension of the new DNA strands by a DNA polymerase enzyme. As a result, PCR can not only extract DNA but also provide sufficient quantities for subsequent analysis, such as sequencing, genotyping, or comparison to known samples.

While electrophoresis is a technique used for separating and analyzing DNA fragments after amplification, it is not directly involved in the extraction process itself. Chromatography and gas chromatography are methods primarily used for separating and analyzing chemical substances, and they do not apply to DNA extraction. In summary, PCR is the most relevant and effective method for obtaining usable DNA from various samples in forensic applications.