The process that separates DNA fragments by size is called gel electrophoresis. In this technique, DNA samples are placed in a gel matrix and subjected to an electric current. The DNA fragments, which are negatively charged, migrate through the gel towards the positive electrode. Smaller fragments move faster and farther through the gel than larger ones, allowing for size-based separation. This method is commonly used in genetics for various applications, including DNA profiling, cloning, and sequencing.