Laboratory 4j
Using Gel Electrophoresis to Study DNA
Molecules
Background
Gel electrophoresis is one of several ways that molecules are studied in labs. The technique
uses a gel and an electric field to separate molecules based on size, shape, and/or charge. Most
frequently, samples of nucleic acids (DNA and RNA) and proteins are analyzed using gel
electrophoresis.
DNA molecules in solution have a net negative charge due to their phosphate groups. Because
of the negative charge, DNA molecules are attracted to the positive end of a “running” gel box.
The agarose gel material acts as a molecular sieve separating longer DNA strands from shorter
ones, thus separating the molecules based on their size.
YX