Southern Blotting Gel Restriction enzyme Human Larger DNA Gene of interest fragments Smaller DNA containing the gene of interest is extracted The fragments are separated according to size by from human cells and cut into fragments by gel electrophoresis.Each band consists of many restriction enzymes. copies of a particular DNA fragment.The bands are invisible but can be made visible by staining. Figure 9.15.1 Southern Blotting Figure 9.15.1