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DNA electrophoresis separates DNA molecules by length using an electric field and gel. Restriction enzymes cut DNA, which is mixed with a dye or radioisotope and separated by electrophoresis. Gel electrophoresis can identify genetic traits, isolate DNA strands, and create genetic profiles for identification. The process has been in development since the 1930s and was first performed in the 1970s.
DNA electrophoresis is a method used to sort DNA molecules by length. Pieces of DNA are suspended in a tray of gel and subjected to an electric field, which causes them to migrate to one end of the tray. The DNA separates into bands, with the distance from the electrode corresponding to the length of the strand. The technique plays a role in identifying genes for disease diagnosis and other forms of genetic research.
The DNA to be studied is split into single strands using restriction enzymes that cut the DNA at specific, known places. The DNA is mixed with a dye or a radioisotope which will allow its location in the gel to be identified. The single strands are then separated from each other by DNA electrophoresis. The process begins by injecting the separated genetic material into wells that have been cut into the end of a gel plate.
An electric field is then applied to the gel plate. DNA has a negative electrical charge and is attracted to the positive electrode. The gel resists the DNA as it moves; smaller pieces move more easily through the pores of the gel and therefore travel farther. Given a known gel preparation and electrical application, the length of a segment can be determined very accurately from the distance it travels. It can then be cut from the gel using a scalpel.
If the fragments to be separated are very short, a polyacrylamide gel is used. For longer segments an agarose gel is used. Agarose is made from seaweed, while polyacrylamide is a synthetic polymer. Agarose gels are much less dense than polyacrylamide gels and allow larger molecules to pass through. For very long segments of DNA, a recently developed method called pulsed-field gel electrophoresis must be used. This process uses an electric field that constantly undergoes subtle changes in direction to keep the very long filaments oriented correctly as they move through the agarose.
Gel electrophoresis can be used to identify the presence of DNA strands of known length. It can then be used to determine the existence of certain genetic traits or diseases within a given individual. DNA electrophoresis can also be used to isolate DNA strands for recombination as part of a genetic engineering project. It can also be used to create a genetic profile of an individual for identification purposes, such as in paternity testing or forensics.
DNA electrophoresis was first performed in the 1970s. Gel electrophoresis has been used to separate proteins long before it was applied to genetic material. The process has been in development since the 1930s, with preliminary research dating back to the 1800s. Swedish biochemist Arne Tiselius is sometimes credited with its invention.
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