How to Prepare and Load a Standard DNA Ladder

Review the materials needed including small plastic tubes or 96-well plates, and understand that standard NEB DNA ladders are concentrated solutions requiring dilution and loading dye before use. Learn that approximately 6 µl of prepared ladder mix is needed per gel lane.

Add 4 µl of water to a tube, then add 1 µl of 6X purple loading dye without SDS. Mix by flicking the tube and spinning briefly to combine.

Add 1 µl of the DNA ladder to the diluted loading dye mixture. Mix again by flicking and spinning briefly to gather the prepared ladder at the bottom of the tube.

Slowly pipette the 6 µl of prepared DNA ladder mix into the desired well on the gel. The ladder is now ready for gel electrophoresis.

Prepare a 1X dilution of 6X purple loading dye in advance by diluting with water. For each gel lane, add 5 µl of the 1X dye dilution to a microfuge tube, then add 1 µl of DNA ladder. Mix by flicking and spinning.

Never dilute the DNA ladder in water without loading dye present, as this can cause DNA fragments to denature. Alternatively, use TE buffer instead of water to prevent DNA denaturation.

Learn that NEB also offers pre-made ready-to-load DNA ladders that require no dilution or dye addition. Simply invert the vial to mix and load directly onto the gel for convenience.