Gel Electrophoresis

Gel Electrophoresis


Gel electrophoresis is a method used to separate and visualize DNA fragments.  Below are some common facts, terms, and definitions related to gel electrophoresis.  


1. Gel Electrophoresis- a process that uses electricity to separate charged molecules, such as DNA fragments, RNA, and proteins, on a gel slab.

2. Agarose - a carbohydrate from seaweed that is widely used as a medium for horizontal gel electrophoresis.

3. Polyacrylamide- a polmer used as a gel material in vertical electrophoresis; used to separate smaller molecules, like proteins and very small pieces of DNA or RNA.

4.  Steps in the Gel Electrophresis Process

        a) Solution is poured into gel trays

        b) Plastic comb is placed in the hot liquid gel so that tiny rectangular sample wells are made as the gel cools in the mold

        c) Solidified gel is placed in teh box covered in buffer solution

        d) When power is turned on electric current runs into the gel box and electric filled is established between positive and negative   electrodes

        e) Sample of charged molecules is loaded into sample wells

        f) When power is turned on, electric field is established

5. Agarose is most commonly used when separating pieces of DNA. These gels are made at a specified concentration by mixing some mass of powdered agarose with some volume of buffer. Concentration of a gel is of critical importance. Agarose molecules in solution, the more strands intertwine to make the strainer. It is most plasmid and restriction digestion fragments separate well.

6. Buffer- a solution that acts to resist a change in PH when the Hydrogen ion concentration is changed

7. Strains are used to reveal a variety of nucleic acid samples

8. Ethidium bromide- a DNA stain (indicator); glows orange when it is mixed with DNA and exposed to UV light; abbreviated E+Br

9. Methylene blue- a straining dye indicator that interacts with nucleic acid molecules and proteins, turning them to a very dark blue color


Frequently Asked Questions and Answers:

1. What agarose gels can be used to study what size of DNA fragments?

Medium to large sizes of DNA.

2. If Agarose gel material is labeled 1%, what does the 1% refer to?

1% represents how much agarose is present in the gel mold.

3. What causes molecules to be separated on an agarose gel?

The electric currents.

4. Name two common DNA stains that are used to visualize DNA on agarose gels.

Ethidium Bromide and Methylene Blue


C. Davis©2007


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