DNA Ladders

DNA ladder or Gene ladder, also known as gene ruler, consists of purified DNA bands which span from a 100 base pair to a 1000 base pair or even higher, depending on the size of the ladder. It is used to identify the molecular weight of an unknown linear fragment of the DNA when loaded and run in agarose gel electrophoresis, along with the test samples. A typical pack has 250 micrograms of the mass at 1 microgram/microliter concentration. Generally, one microliter is loaded for running on a single gel. The ladder is sensitive and to prevent degradation it is stored at -20 degrees. A standard curve may be drawn to quantify DNA.