What technique separates nucleic acids or proteins by size and charge using an electric field in a gel?

• A. Spectrometry
• B. Gel Electrophoresis
• C. Chromatography
• D. PCR

Answer: (B)

Gel electrophoresis uses a gel as a porous matrix and an electric field to move charged molecules. The electric field pulls molecules toward the opposite electrode, and their movement through the gel depends on size and charge: smaller fragments slip more easily through the pores and thus travel farther, while larger ones move more slowly. For nucleic acids, the backbone gives a uniform negative charge, so size largely governs how far DNA fragments migrate. For proteins, you can separate by size as well, especially with SDS-PAGE, which coats proteins with a uniform negative charge so migration mainly reflects molecular weight.

This method is commonly used to estimate fragment sizes, check PCR products, or assess DNA fingerprints and protein purity. It’s not spectrometry, which analyzes mass or structure without separating in a gel, nor chromatography, which relies on interactions with a stationary phase in a column, nor PCR, which amplifies DNA rather than separating it by size.