Gel electrophoresis is used for which of the following purposes?

• A. A method to measure RNA expression levels
• B. A method to sequence DNA
• C. Procedure used to separate and analyze DNA fragments by placing a mixture of DNA fragments at one end of a porous gel and applying an electrical voltage to the gel
• D. A method to clone DNA

Answer: (C)

Gel electrophoresis is a technique that separates DNA fragments by size by placing a mixture of fragments in a porous gel and applying an electric voltage. DNA is negatively charged, so it moves toward the positive electrode; smaller fragments navigate the gel pores more easily and travel farther than larger ones. This separation lets you analyze fragment lengths and assess results like PCR products or restriction digests. It isn’t used to measure RNA expression, which relies on RNA-specific methods, nor to sequence DNA, which requires sequencing technologies, nor to clone DNA, which involves inserting DNA into a vector and propagating it.