Gel electrophoresis

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Gel electrophoresis machine. The mixture is placed in the well. The gel is held by plates. The electric field applied 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 the application of an electric field through the gel.

The word electrophoresis comes from –electro, because an electric field is used, and –phoresis, which means movement.

Gel[change | change source]

The gel is made up of large and branched molecules called polymers. The amount of branches in the gel determines how easy molecules squeeze through, depending on their size.

If there are a lot of branches, only small molecules can pass through. If there are few branches, big molecules can pass through. This is similar to a filter, if the hole is small, only small things can go through the hole.

Charge of the molecule[change | change source]

Block of gel seen under ultraviolet (UV) lamp. The bands are colored red.

If a molecule has a big charge, its attraction to the opposite charge is also big. In gel electrophoresis, molecules with big charges are going to move faster.

If a molecule charge is very small, the attraction is going to be small. This means the molecule is going to move slowly in the gel. If the molecule does not have a charge, it will not move.

Visualization[change | change source]

After the separation, there are two common ways to see where the molecules moved to (bands). One way see the bands is to stain the gel with a dye. The stain makes the places where the molecules moved to appear as colored bands. The other way is observe the gel under an ultraviolet lamp to see the bands.

Applications[change | change source]

DNA separation[change | change source]

Gel electrophoresis is the most commonly used technique to study DNA. DNA is a very large molecule that contains genetic information. DNA can be broken down to smaller pieces of different sizes and these pieces are then separated using gel electrophoresis.

Protein separation[change | change source]

Proteins are large and complex molecules made of smaller pieces called amino acids. Proteins can be studied by gel electrophoresis in two ways. One way is to take a mixture of proteins and separate them in the gel. The other way is to breakdown a single protein into smaller pieces. The smaller pieces can then be separated in the gel.

Medicine[change | change source]

In medicine, there is a special type of electrophoresis called iontophoresis. Iontophoresis uses the same idea of gel electrophoresis to deliver drugs into the human body through the skin without using needles to inject the drug.