Gel Electrophoresis is the movement of small particles (DNA, RNA, or proteins) through a gel facilitated by the application of electricity. Gel electrophoresis separates DNA strands by size. The gel acts as a sieve to slow the progress of the molecules. Longer strands move slower than shorter strands and therefore move less distance. So when you read a gel you move from the area farthest from where the samples were placed in the gel (positively charged, attracting the smallest fragment) to the area closest to where samples were put into the gel to get your sequence. Though gel electrophoresis separates molecules primarily by size, it is also influenced by molecule shape and charge density.
Gel Electrophoresis has 8 basic steps:
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gel - A semi-solid colloidal system consisting of a solid dispersed in a liquid.
electro- - denoting processes carried on by electrical means, or the application of electricity
-phoresis - the movement of small particles by some agency (definitions taken from the Oxford English Dictionary online - www.oed.com)>