What is Gel electrophoresis?
[[File:Electrophoresis - Filling 1D gel wells with proteins mixture.jpg|thumb|'''Gel electrophoresis machine'''. The mixture is placed in the well. The gel is held by plates. The [[electric field]] causes the gel to have a positive and negative side on opposite ends]] '''Gel electrophoresis''' is a technique used to separate mixtures like [[DNA]] and [[proteins]]. The separation is based on how positively or how negatively charged a molecule is, and its size. Gel electrophoresis uses a [[gel]] (like [[gelatin]]) and an [[electric field]] is put through the gel. The word electrophoresis comes from –'''electro''', because an electric field is used, and –'''phoresis''', which means movement. == Gel == The gel is made up of large and branched molecules called [[polymers]]. The amount of branches in the gel determines how easily molecules can squeeze through, depending on their size. If there are a lot of branches, small molecules will be able to move through easily while big molecules will move through slowly or not at all. If there are few branches, both big and small molecules can move through more easily. == Charge on the molecule == [[File:AgarosegelUV.jpg|thumb|Block of gel seen under [[ultraviolet]] (UV) lamp. The bands are colored red]] If a large molecule has a big charge, its attraction to the opposite charge is also large. But, since the molecule is large, it will have a difficult time moving through the thick gel. In gel electrophoresis, large molecules are going to move slower. A small charged molecule will move through the gel more easily. Shorter molecules move faster and move further than longer ones because shorter molecules get through the pores of the gel more easily. This phenomenon is called ''sieving''.<ref>Sambrook J. & Russel D.W. 2001. ''Molecular cloning: laboratory manual''. 3rd ed, Cold Spring Harbor Laboratory Press, NY.</ref> If the molecule does not have any charge, it will not move. == Visualization == After the gel has been run by applying the electric field, you can look