Gel electrophoresis is used in many areas of biotechnology and forensics. It is based on the concept that mixtures of substances can be separated by electrical force. The direction and speed of migration through the field is dependent on several factors. All substances are made of molecules that can be positively charged, negatively charged or neutral. These characteristics can be used to separate molecules when they are placed in a gel that has an electrical field. The gels generally used are made of agarose, a purified version of agar used in making bacterial plates. These gels are a porous material that acts as a molecular sieve through which smaller molecules can move more easily than larger ones. They move toward the opposite charged side of the gel with smaller pieces of DNA moving farther from the well compared to larger pieces. In this activity, students will identify separate molecules in a mixture by exposing them to an electric field, determine the charge and size of a molecule by its movement in a gel, and explain the importance of electrophoresis as a tool in biotechnology. This activity may be downloaded in Microsoft Word Doc file format.
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