Gel electrophoresis

[CFS14]

I am planning to do a project I found on your site called Building your own tool for identifying DNA. Looking through the procedure I noticed that you said to pour the buffer, then remove the comb and then place the dye in the wells. My questions are :

1) Will the buffer not fill up the wells when it is poured first?
2) How will the samples then be placed in the wells?
Could you please clarify this for me please.

[deleted-141593]

Hi there,

The buffer will indeed fill the wells, but you can still fill them with sample by placing a pipette tip in the well and slowly releasing. The loading dye in the sample is there to help you watch what you are doing and make sure the sample stays in the wells. Try watching this demonstration: https://www.youtube.com/watch?v=tTj8p05jAFM

Cheers,
Colin

[CFS14]

Thank you for the helpful video. If the student does not have access to micropipettes, can they use a syringe or dropper instead?

[deleted-141593]

As long as the tip of whatever you are using fits in the well it should be ok. If the tip is too large then some sample may be dispersed and not make it into the well.

Cheers,
Colin

[SciB]

Hi,

I would strongly recommend borrowing a micropipettor to load the samples into the wells.

Your question was very well put. I have seen many students lose their samples by pipetting them into the wells TOO fast. A micropipettor allows you to slowly add the samples so that they do not spill out of the well. Your sample is denser than the running buffer so it will sink into the well, but if you pipet too fast or your finger slips on the ejector the sample may be 'blown' out of the well.

A dropper with a rubber bulb does not give you the kind of control you get with a pipettor. A 1 cc syringe might work but in my experience it takes a good push to get the plunger moving and then it is apt to move too fast and blow the sample out of the well.

As Colin said in his post, when you load the samples you need to put the tip INTO the well below the surface of the buffer and a dropper usually has too wide a tip to fit into the well. A syringe needle is small enough; just be careful that you don’t slip and poke a hole in the bottom of the well.

Let us know what you decide to do and how it comes out.

Good luck!

Sybee

[yvetteds]

I have done this many times over the course of my science teaching.. one more thing to be careful of as you load the wells is not to put the tip of the pipet into the wells too far. I have seen many samples lost when a hole is put accidentally into the bottom of the well when a student pushes down too far into the well.
We always provided practice gels with practice loading dye before loading the real sample. It does take a bit of practice and a steady hand

The trick is to get enough sample into the wells. If not enough then you might not be able to 'see' your results later when you use the visualization dye.

Good luck!