RNA is also composed of bases and five-carbon sugar and phosphate molecules. In agarose gel electrophoresis, agarose plays a screening role, and different RNA charges and molecular sizes are different. When passing through the agarose electric field, RNA will run to the other end of the electrode according to the positive and negative attraction. Because of the different molecular sizes, the mesh of the screen is fixed, so RNA with different sizes will fall in different positions, thus forming a straight electrophoresis band with different thickness.