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Gel electrophoresis is a technique for separating molecules (such as proteins, DNA, or RNA fragments) according to the size and involves the migration of particles in a given gel during application of a potential difference. Linear DNA molecules become separate according to size when subjected to an eletric field through a gel matrix. This technique allows biologists measure the size of the DNA fragments without sequencing them since, as the migration speed is a function of fragment length, the measure of the distances of migration can be used to estimate these fragments sizes. The sequencing gel systems utilize a source of high voltage (1500-3000V). After electrophoresis is complete, the DNA molecules can be visualized by staining the gel with fluorescent dyes. The technique was first applied to population genetics in 1966, by Lewontin and Hubby.
How it works
Nucleic acids have a phosphodiester backbone meaning that they carry numerous negatively charged phosphate groups, so that, when present in an electric field they tend to migrate toward the positive electrode. When migrating by a porous gel, the nucleic acid molecules can be separated according to size. The molecules to be sorted are dispensed into a well or chamber in the gel material. The gel is placed in an electrophoresis chamber, which is then connected to a power source.
When electrical current is applied, the large molecules move more slowly through the gel, while the smaller molecules move more quickly.
After electrophoresis has been completed, the molecules in the gel can be stained with dye to make them visible. The DNA may be visualized using ethidium bromide, which, when intercalated into DNA, is fluorescent under ultraviolet light.
Types of gel
- ↑ Conoley, Chris; Hills, Phil (2008). Chemistry (3rd ed.). London: Harper Collins Publishers. p. 377. ISBN 978-0-00-726748-4.
- ↑ 2.0 2.1 Watson, James D.; Baker, Tania A.; Bell, Stephen P.; Gann, Alexander; Levine, Michael; Losick, Richard (2004). Molecular Biology of the Gene (5th ed.). San Francisco, CA: Pearson, Benjamin Cummings. p. 648. ISBN 0-8053-4635-X.
- ↑ Pevzner, Pavel A. (2000). Computational Molecular Biology: An Algorithmic Approach. The MIT Press. p. 273. ISBN 0-262-16197-4.
- ↑ Alphey, Luke (1997). DNA Sequencing:From Experimental Methods to Bioinformatics. New York: Springer/Bios Scientific Publishers. p. 53-62. ISBN 0-387-91509-5.
- ↑ Lester, Lane P.; Bohlin Raymond G. (1989). The Natural Limits to Biological Change (2nd ed.). Dallas, Texas: Probe Books. p. 61. ISBN 0-945241-06-2.
- ↑ 6.0 6.1 Strachan, Tom; Read, Andrew P (2011). Human Molecular Genetics (4th ed. ed.). New York: Garland Science. p. 204-205. ISBN 978-0-8153-4149-9.