What process separates DNA fragments according to size?

The process that separates DNA fragments according to size is electrophoresis. This technique utilizes an electric field to propel charged particles, which in the case of DNA, are negatively charged due to their phosphate backbone. When a sample containing DNA fragments is placed in a gel matrix, typically agarose or polyacrylamide, and an electric current is applied, smaller DNA fragments move more easily through the gel than larger fragments. As a result, the DNA fragments are separated based on their size, allowing for analysis and visualization.

Electrophoresis is widely used in molecular biology for various applications, including DNA fingerprinting, genetic analysis, and the separation of PCR products. It is a fundamental technique in laboratories for analyzing and manipulating genetic material due to its effectiveness and reliability in size-based separation.

The other options listed serve different functions. Chromatography is primarily used for separating and analyzing mixtures of compounds based on their chemical properties. Mass spectrometry is employed for identifying compounds and determining their molecular weights, often involving ionization. Fluorescence polarization immunoassay is a technique used for detecting specific analytes in a sample, usually for immunological studies, rather than for separating DNA fragments.