Used in molecular biology laboratories for estimating the size of DNA fragments during gel electrophoresis. It serves as a reference standard by providing a series of DNA fragments of known lengths. When loaded alongside experimental samples on an agarose or polyacrylamide gel, the ladder allows researchers to compare the migration distance of unknown DNA fragments to the ladder bands, enabling accurate size determination. Different ladder formulations cover various size ranges, making them suitable for applications such as PCR product analysis, restriction enzyme digestion verification, and genomic DNA assessment. Its consistent band pattern also helps in monitoring electrophoresis run conditions and gel resolution.