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Hello, i am doing a project on gel electrophoresis and just had a few questions.

-What is the basic process?
-What is it used for? What fields?
-How is the gel prepared/made?
-How are the DNA segments tracked?
-Could the average person conduct their own gel electrophoresis experiment?

Any answers to any of these questions would be greatly appreciated.

Thank You
Answer 1:

Great questions! Electrophoresis is a technique used by many scientists, but not very well known by many students, so thanks for asking!

Gel Electrophoresis is basically a technique used to separate nucleic acids (the material of DNA and RNA) or proteins according to their relative sizes. Say a scientist has a tube with a mixture of different sizes of DNA or protein, and would like to separate one size or one piece of this mixture away from the rest of the sizes or pieces. The best way to do this is gel electrophoresis.

The term electrophoresis comes from electro- and phoresis. "Phoresis" means basically "movement" and "electro" refers to the electrical field that's used to separate the nucleic acids or proteins. In overview; samples are run through a gel network, moved by an electric field, and will separate according to size. After the samples are separated, they can be analyzed.

The gel serves as a solid mesh to support the biological sample as is it separated by the electrical field. The gel is like a kitchen sponge, but with a microscopic network of holes and connections. For DNA samples, generally a gel is made like you would make jell-o, by heating up a polymer (agarose) with liquid, poring it into a mold, and allowing the network to solidify. (Fun fact: agarose is made from seaweed, and is actually in some products like toothpaste and gummy snacks!) For protein samples, generally a finer network (smaller holes) is required, so a gel is made of a different polymer (acrylamide).

Once the gel has solidified, it is covered in a liquid (buffer) through which an electric current can pass. Samples are set into the gel, usually in small niches, or "wells". The protein or nucleic acid will generally be mixed with a dye to see the samples, and a component to help the sample sink in the well, and to not mix with the (buffer). An electric current is applied to the gel and samples, by having a current applied to a cathode nearest to the samples, and an anode at the other end of the gel. Nucleic acids are negatively charged, and will move to the positively charged end of the gel. Proteins have different shapes and charges, and are treated before electrophoresis to have approximately the same shape (straightened out) and uniform negative charge.

As the sample moves through the gel, the mix of sizes starts to be separated. You can imagine a group of creatures running through a dense forest; the smallest critters can maneuver the fastest through the trees, while the giants take much longer to navigate through!

After the sample has run the length of the gel, the electrical force is stopped, and the samples are visualized as "bands" or short lines on the gel, kind of like a ladder. A sample of known sizes in run simultaneously with the other samples. This allows for comparison and determining the approximate size the unknown sample bands. Nuclei acids can be visualized by staining with a molecule (ethidium bromide) that slots between the nucleic acid "base pairs" and will glow under ultra violet light (like a black light). Protein is generally stained with a dye. The separated sample bands can then be photographed, transferred to another material to be further characterized, or single bands can be cut out from the gel and the sample purified from the gel!

Gel Electrophoresis is used in many fields, including molecular biology, biochemistry, forensics, and genetics; it is used frequently in health diagnosis.

The compounds used in this technique can be toxic, and the electrical field could be harmful if not used properly. But, if people are trained, and have proper supervision and equipment, they could run a successful gel electrophoresis. In certain programs and classes, high school students frequently learn and apply this technique!



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