How do I read agarose gel electrophoresis?

Reading gel electrophoresis results involves visualizing agarose gels, typically done using a UV light box in a dark room or a self-contained light box connected to a camera. In either method, UV light is passed through the gel from below, causing the DNA bands to fluoresce due to the intercalating dye bound to them. These fluorescent bands can be photographed using a camera equipped with a UV filter. Marker ladders, which come with a guide indicating the size of each band, are used to compare and determine the sizes of the bands in the sample lanes. 

The relative DNA concentration between samples can also be compared when reading gel electrophoresis results as higher concentrations result in brighter bands.