Gel electrophoresis
On Tuesday you will be separating out your PCR products according to size by using agarose gel electrophoresis. This technique relies on the fact that DNA has a net negative charge (think of all those phosphates along the phosphodiester backbone). So if you put DNA in an electric field it will move towards the positive electrode .... in practice we put the DNA into a jelly-like material called agarose, and the DNA moves through this agarose when an electric current is passed through it. The cool thing is that large DNA fragments will have a hard time getting through the gel, so they will travel slowly. Small DNA fragments, on the other hand, have much less trouble getting through the gel so they move faster. This means that we can use this technique to separate DNA fragments based on their size....... Here is what happens with agarose gel electrophoresis with a step-by-step description underneath: image taken from: http://www.all-science-fair-projects.com/science_f