What is a ladder/standard/marker used for in electrophoresis?

In electrophoresis, a ladder, standard, or marker serves as a reference point to determine the size of unknown DNA or protein samples. These markers contain fragments of known sizes, allowing for the comparison of the migration distance of the samples being tested against these known sizes. By observing where the samples fall in relation to the ladder, researchers can estimate the size of the DNA or protein in their own samples based on how far they have migrated through the gel.

This practice is essential for various applications, including verifying the success of DNA digestion or amplification techniques. Accurately determining the size of DNA or protein is crucial in many molecular biology procedures, making the use of a ladder a fundamental aspect of electrophoresis.