question: What analytical technique, using stained gel, can separate dna fragments or rna molecules and proteins?
distractor3: static electrophoresis
distractor1: microwave electrophoresis
distractor2: surface electrophoresis
correct_answer: gel electrophoresis
support: Gel electrophoresis is an analytical technique used to separate DNA fragments by size and charge. Notice in Figure below that the "gels" are rectangular in shape. The gels are made of a gelatin-like material of either agarose or polyacrylamide. An electric field, with a positive charge applied at one end of the gel, and a negative charge at the other end, forces the fragments to migrate through the gel. DNA molecules migrate from negative to positive charges due to the net negative charge of the phosphate groups in the DNA backbone. Longer molecules migrate more slowly through the gel matrix. After the separation is completed, DNA fragments of different lengths can be visualized using a fluorescent dye specific for DNA, such as ethidium bromide. The resulting stained gel shows bands correspond to DNA molecules of different lengths, which also correspond to different molecular weights. Band size is usually determined by comparison to DNA ladders containing DNA fragments of known length. Gel electrophoresis can also be used to separate RNA molecules and proteins.