Gel electrophoresis separates molecules of different sizes by applying an electric current to a gel matrix containing DNA, RNA, or protein samples. Samples are added to wells and separated based on size. This technique is used in various fields of biological research.
In gel electrophoresis, an electric current is applied to a gel matrix that contains DNA, RNA, or protein samples. The electric current moves the protein or nucleic acid molecules through the gel, allowing molecules of different sizes to separate. This technique is used to detect or isolate molecules of a particular size from a mixture of nucleic acids or proteins.
The first step in the gel electrophoresis protocol is to place a block of gel in a small reservoir. The gel consists of a compound that forms a solid at room temperature and has a neutral charge. The reservoir that holds the gel block is then filled with enough of a special gel electrophoresis buffer solution to completely cover the gel.
At one end of the gel block is a series of small wells. A small amount of DNA or protein sample is added to each well. Each individual well contains a test sample with an unknown mixture of nucleic acid or protein. An additional well contains a control sample with a mixture of nucleic acid or proteins of known size. Each sample, including the control, was mixed with a dye to help identify sample locations once electrophoresis was completed.
Once all of this setup work has been completed, electrophoresis is started by applying an electric current to the holding tank in which the gel is located. The electric current pushes the sample molecules through the gel, at a speed proportional to the size of the molecule. Smaller molecules travel rapidly through the gel, while larger ones travel slowly. As the molecules travel, they separate on the gel based on their size.
When the dye reaches the other end of the gel, the electric current is removed and the gel is stained with a solution that enhances the color of the dye. Finally, the gel is “read” by measuring the distance traveled by each molecule during the time allowed for electrophoresis. This information can be used to calculate the size of each molecule in each of the samples.
There are several types of experimental techniques using electrophoresis. In a Southern blot, agarose gel electrophoresis is used to isolate fragments of DNA or RNA. Western blot uses polyacrylamide gel electrophoresis to isolate proteins from a mixture. Each of these techniques is used to search for a certain predefined sequence of nucleic acid or protein. Electrophoresis and blotting techniques are used in many areas of biological research as well as in the medical and forensic sciences.
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