Which technique is commonly used to separate DNA fragments based on size?

Gel electrophoresis is widely used to separate DNA fragments based on size due to its effectiveness in utilizing an electric field to propel charged molecules through a gel matrix. When DNA is loaded into a gel and an electric current is applied, the negatively charged DNA molecules migrate towards the positive electrode. Smaller fragments of DNA move through the gel more easily and quickly than larger fragments, resulting in separation based on size. This technique allows researchers to analyze the sizes of DNA fragments, which is crucial in various applications such as cloning, DNA fingerprinting, and analysis of PCR products.

Other methods mentioned do not serve this specific purpose. Chromatography is typically used for separating mixtures based on the different interactions of compounds with a stationary phase and a mobile phase, making it more suitable for liquids and small molecules rather than DNA fragments. Western blotting is a technique used for detecting proteins rather than nucleic acids, and DNA microarrays are designed for analyzing gene expression or genotyping rather than size separation of DNA fragments. Thus, gel electrophoresis stands out as the appropriate choice for separating DNA based on size.