n Southern blot hybridization, a labeled probe DNA is applied to a population of DNA molecules that have been separated by size using gel electrophoresis. The goal of this procedure is to: Determine the molecular weight of the DNA molecules on the gel. Identify a DNA molecule whose sequence is complementary to the probe. Ensure that fragments of different sizes separate on the gel. Identify a DNA molecule that contains the same label as the probe. Visualize all DNA molecules on the gel.