Agarose gel electrophoresis

1. Cast a gel
2. Place it in gel box in running buffer
3. Load samples
4. Run the gel
5. Image the gel

The amount of agarose to use in your gel depends on the DNA in question. Use the following table as a rough guide:

Agarose Concentration (g/100mL)	Optimal DNA Resolution (kb)
0.5	1 - 30
0.7	0.8 - 12
1.0	0.5 - 10
1.2	0.4 - 7
1.5	0.2 - 3

1. Measure out the appropriate mass of agarose into a beaker with the appropriate volume of buffer (see the documentation for your gelbox -- 50mL makes a good, thick gel for a 7x10cm gelbox).
2. Microwave until the agarose is fully melted. This depends strongly on your microwave, but a 90 seconds at full power or 3 minutes at half power seem to provide decent results. As long as you do not burn the agarose and nothing bubbles over, this step is robust.
3. Let the agarose cool on your bench until touching the bottom of the beaker with your bare hand doesn''t burn you (~5 minutes for a 50mL gel). At this point add your DNA stain, e.g., ethidium bromide. The beaker will cool unevenly (surface first), so you must be careful not to cause ripples and bubbles.
4. While the solution is cooling, seal the open edges of your gel box with one long piece of masking tape on each side. Make sure it is sealed well or the gel will leak.
5. Pour the agarose solution into the taped gelbox. Carefuly pop or shove to the side any bubbles, put in the comb, and let it cool for about 30 minutes, until the gel is solid.

If your gel is at all purple, and you are using ethidium bromide as the DNA stain, you need to decrease your concentration by at least a factor of ten.

• TAE - better resolution of fragments >4kb;
• TBE - better resolution of 0.1-3kb fragments; TBE is better suited for high-voltage (>150V) electrophoresis than TAE because of its higher buffering capacity and lower conductivity;
• SB - Sodium borate - low heat generation with good resolution. Allows for higher voltage (250-200V) electrophoresis without melting.

dye	0.5-1.5% agarose	2.0-3.0% agarose*
xylene cyanol	10''000-5000 bp	750 bp
bromophenol blue	400-500 bp	100 bp

*sieving agarose