Science Fundamentals: Agarose Gel Electrophoresis

Science Fundamentals is a series on foundational concepts in science. My goal is to give you the tools to critically think and discuss scientific concepts in everyday language and without the grind of actually getting a Ph.D. Be sure to check out the other installments in the series. I have done DNA, and Polymerase Chain Reaction so far.

This is a quick follow up to the PCR article, to flesh out the end of that line of thought. After you run a PCR, you have to determine if the PCR amplified the DNA you wanted. To do this, we typically run agarose gels.

Agarose is modified agar, which is jello made from seaweed. You can actually buy this in stores these days, usually as vegan jello. I have even seen cakes made out of it, which are usually very pretty, but lack taste. If you want to check these out, I believe they are called dew drop cakes.

These agarose gels are used to separate DNA by size. An electric current is run through the gel, pushing the DNA through the gel. This works as DNA is a charged molecule, and so it responds to electrical currents. As the electricity pulls the DNA through the gel, the agarose acts like an obstacle course for the DNA. Larger pieces of DNA move more slowly through the obstacle course, but smaller pieces are more nimble and can move faster. Thus the smaller bits of DNA move further in the gel, and the larger ones stay near the top of the gel.

Procedure