what is the function of a ladder in gel electrophoresis

The function of a ladder in gel electrophoresis is to determine the size of DNA fragments by electrophoresis. A DNA ladder is a common reagent used in biotechnology laboratories to size DNA fragments and agarose gels. The ladder is a mixture of DNA fragments of known sizes that are run alongside the sample DNA fragments on the gel. The ladder fragments create a reference for the size of the sample fragments, allowing researchers to determine the size of the sample fragments by comparing them to the ladder fragments. Therefore, the ladder helps to gauge the size of the bands in the sample.