Strands of DNA are cut into small fragments using restriction endonucleases. There are thousands of different restriction enzymes each cutting DNA at a specific sequence or recognition site. A combination of restriction enzymes leaves the micro and mini-satellite regions intact.DNA fragments are then separated by gel electrophoresis. The strands are then separated into single strands and then transferred to a membrane by Southern blotting. Radioactive or fluorescent DNA probes are added. These bind to complementary strands at the correct pH and temperature (DNA hybridisation). X-ray images are taken if radioactive probes were used. U.V. is used to view the DNA if fluorescent probes were used.