Southern blots detect a target DNA sequences through the hybridization of complementary probes. An endonuclease is used to fragment the sample DNA. The DNA fragments are separated by size using gel electrophoresis. The DNA is denatured then transferred onto a membrane using a buffer and capillary action. A probe applied to the fixed membrane is used to detect the target DNA sequence. The probe may be composed of DNA or RNA and is labeled for detection. After washing away excess probe, the membrane is scanned for the presence of the probe label. Southern blotting is used to confirm and characterize gene sequences.