How to load a gel for electrophoresis

Loading DNA or RNA samples for gel electrophoresis takes a little practice. Here are five tips to help your students load gels like pros. 

Rest your elbow on the table while using your dominant hand to operate the micropipette.

1. Brace yourself — you are aiming for a small target.

  • Rest your elbows on your table.
  • Use your dominant hand to operate the micropipette, and use your other hand to steady your pipette by placing a finger on the pipette shaft near where it meets the pipette tip.

2. Check your aim.

  • Place the pipette tip just inside the well.
  • Wiggle the tip side to side to make sure you are in the well. 

3. Don’t puncture the well.

  • Putting the tip too deep in the well will cause the agarose in the bottom of the well to rupture, allowing the sample to leak out.
  • Because the loading dye makes DNA samples more dense than the electrophoresis buffer, DNA dispensed near the top of the well will sink readily into the well.

4. Dispense your sample slowly.

  • Slowly push the plunger steadily down to dispense the sample into the well.
  • If you eject the sample with too much force, it can ricochet out of the well.
  • Stopping at the first stop makes for safer gel loading than pushing the plunger all the way down. Pressing to the second stop may force air out of the pipette tip and displace the sample.

5. Hold the plunger down until your tip is fully removed from the well and the buffer.

  • If you release the plunger before you remove the tip from the well, you will suck your sample back up.
  • If this happens, just dispense the sample back into the well. 

For a full tutorial on micropipetting technique, check out these resources.


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