Definition of Molecular weight ladder

Molecular weight size marker (ladder) is also referred to as a protein, DNA or RNA ladder. These ladders are a set of standards that are used to identify the approximate size of a molecule run on either an agarose or polyacrylamide gel during electrophoresis. The approximate size calculation is based on the principle that molecular weight is inversely proportional to the migration rate of the molecule through a gel.

2D gels

Agarose gel


Camera lens focal lengths

CCD camera