Which technique uses an electric field to separate DNA in agarose?

Electrophoresis is the technique used to separate DNA in agarose using an electric field. In this process, DNA molecules are placed in a gel matrix made of agarose, which acts as a sieve. When an electric current is applied across the gel, the negatively charged DNA fragments migrate towards the positively charged electrode due to the electric field. The size of the DNA fragments affects their mobility through the gel; smaller fragments move faster and farther than larger ones. This differential movement allows for the separation of DNA fragments based on their size, making electrophoresis a critical technique in molecular biology for analyzing DNA.

Centrifugation, chromatography, and filtration each operate on different principles that do not involve the use of an electric field to separate molecules based on size or charge. Centrifugation separates components based on density by spinning samples at high speeds, while chromatography relies on differential affinities for stationary and mobile phases to separate components in a mixture. Filtration is a physical separation method that uses a barrier to separate particles based on size but does not involve the movement of charged molecules under an electric field. Thus, electrophoresis is specifically designed for the efficient separation of DNA, making it the correct choice.