Which method is commonly used to separate DNA fragments based on size and charge?

Gel electrophoresis is a technique that separates DNA fragments based on their size and charge. In this method, an electric current is applied to a gel matrix through which the DNA is loaded. Because DNA molecules have a negative charge due to their phosphate backbone, they migrate toward the positive electrode. Smaller fragments move through the gel more easily and thus travel faster than larger fragments. This results in the separation of the DNA into distinct bands according to size, allowing researchers to analyze the fragments for various purposes, such as genetic profiling, cloning, or sequencing.

Other methods listed serve different functions: polymerase chain reaction is utilized for amplifying DNA, centrifugation is used for separating components based on density but not typically for DNA size separation, and chromatography is generally used for separating mixtures of substances rather than specifically for DNA fragments. Thus, gel electrophoresis is the method specifically designed for effectively separating DNA based on size and charge.