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Thermo Scientific MassRuler Express HR Forward and Reverse DNA ladders are specially designed for fast and reliable DNA quantification in short separation distances under various electrophoresis conditions (see Table 1). In the forward versions, the mass of each DNA fragment is directly proportional to the fragment size, whereas in the reverse versions, the mass is inversely proportional to fragment's size.
The intensity of the fragment in each ladder is calibrated against a standard that guarantees the precise quantity of each band. The ladders are mixtures of chromatography-purified, individual DNA fragments.