Gel Electrophoresis

Smaller DNA molecules move farther than their larger counterparts
Smaller DNA molecules move farther than their larger counterparts


What is it?:
Gel Electrophoresis is a process used to seperate fragments of DNA by running an electric current through them. It's used as a tool to find and compare DNA coding, mainly in criminal investigations.

How it's done: First, forensic scientists have to extract DNA from a cell. This is done simply by opening the cell and extracting the DNA from the parts of the cell. Next they're put into a special chemical mix of restriction enzymes. Restriction enzymes are special in that they cut DNA along certain base patterns depending on the enzyme used. After they're dyed, they're poured into wells in a gel layer and have an electric current run through them. Since DNA has a negative charge, it moves towards the positive charge. Smaller fragments move faster so they appear at the farther end of the gel, bigger pieces are found closer to the wells.

How it's used: When genetic material (like blood, semen, etc) is found at a crime scene, it's sent to a criminal investigation lab. The DNA is extracted from cells and run through an electrophoresis. Samples of DNA are also taken from suspects and run through the same process. When pieces of DNA line up, investigators know they have a match and they suspect has had something to do with the crime scene

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Concepts of Gel Electropherosis