Agarose gel electrophoresis is primarily utilized for the separation of nucleic acid fragments based on their size. When an electric current is applied to an agarose gel, negatively charged nucleic acids, such as DNA or RNA, migrate towards the positive electrode. The agarose matrix allows smaller fragments to travel faster than larger ones, thereby enabling the determination of molecular sizes of nucleic acids.
The ability of agarose gel electrophoresis to effectively separate these fragments makes it an invaluable tool in molecular biology for applications such as DNA fingerprinting, cloning, and PCR product analysis. While other methods may be employed for separating proteins, agarose gel electrophoresis is specifically designed for nucleic acids and is not commonly used for plasma protein separation, rendering the selection of that option less accurate in the context of this question.