Why is gel electrophoresis used

Different proteins have different sizes, mainly due to the number of amino acid building blocks in their structure. Chemical modifications attached to the protein also affect its size. Different proteins also have different charges. This can result from both the types of amino acid used to construct them, as well as the types of modifications attached to them. Different types of electrophoresis gels are used to provide different types of information. The type of gel you choose therefore depends on the type of question you are asking.

Typically, gels made from polyacrylamide are used to separate proteins on the basis their different sizes. Usually, the proteins are first treated with heat and a chemical called SDS in order to unravel the protein.

SDS is a detergent that gives all the proteins the same overall negative charge so that when an electric current is applied to the gel, separation is only due to the size of the protein.

Electrophoresis is a very broadly used technique which, fundamentally, applies electric current to biological molecules, whether--they're usually DNA, they can be protein or RNA, too It's used in a variety of applications Everything from forensics for determining the identity of individuals that may have been involved in a crime, by linking their DNA pattern, their electrophoresis pattern, to one that's in a database.

The whole basis by which the human genome was done is by something called capillary electrophoresis, by separating DNA into shorter pieces and then running them on these electrophoresis gels which allow the patterns of As, Cs, Ts, and Gs to be elucidated. This treatment makes the proteins unfold into a linear shape and coats them with a negative charge, which allows them to migrate toward the positive end of the gel and be separated.

Finally, after the DNA, RNA, or protein molecules have been separated using gel electrophoresis, bands representing molecules of different sizes can be detected. Related Concepts You have authorized LearnCasting of your reading list in Scitable.

If the liquid is a simple one--such as water with some salts in it--all the DNA molecules move at nearly the same speed. Under those conditions, it is hard to distinguish the tiny disparities in the motion of different kinds of DNA. Usually smaller DNA molecules move faster than larger ones. After a while, the molecules are separated by size.

If the molecules fall into only a few discreet sizes, then bands little rectangles of DNA will appear in the gel. Each of these bands contains DNA strands of a specific size. The human DNA molecules are treated with enzymes that chop them at certain characteristic points, thereby reducing the DNA to a collection of more manageably sized pieces.