1) DNA is digested with a RE, separated by gel electrophoresis.
2) Transferred to a membrane. Same pattern.
3) The blot is incubated with many copies of a probe. This probe will form base pairs with its complementary DNA sequence and bind to form a ds DNA molecule. Radioactive/ enzyme bound (ALP or horseradish per).
4) The location of the probe is revealed by incubating it with a substrate = colored product.