Used in molecular biology and genetics research to estimate 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 run alongside samples on an agarose or polyacrylamide gel, it allows researchers to compare and determine the approximate size of unknown DNA fragments based on their migration distance. 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. The inclusion of colored dyes in some ladders enables real-time tracking of electrophoresis progress.