MCB 3020L Lecture Notes - Lecture 8: Agarose Gel Electrophoresis, Gel Electrophoresis, Ethidium Bromide
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Once the dna sample has been treated and digested by restriction enzyme, sample buffer is added: contains glycerol, which increases the density of a sample, tracking dye, bromophenol blue. Each dna base contains a phosphate group, which carries a negative charge: longer molecule more negative charge. Digested dna is placed into wells near one end of a slab or agarose gel: tae buffer, agarose, and small amount of ethidium bromide, agarose solidifying agent. More agarose- more restrictive of movement of dna fragments- takes longer and creates finer bands. Buffer creates a continuous path of electrical flow. Current is applied with the cathode (-) near the wells containing the dna and the anode (+) on the opposite end. After the gel electrophoresis is complete, these groups of fragments (separated by approximate size) form bands in the gel: these bands would not be visible without the addition of a dye such as ethidium bromide.