In DNA fingerprinting, the hybridised strands are detected by

Detection of hybridised DNA fragments is done by autoradiography.

DNA labeled with radioactive substance is called radioactive probe. The probe is a single-stranded DNA molecule that is complementary to the gene of interest in the sample under study. The probe attaches by base pairing to those restriction fragments that are complementary to its sequence. After the probe hybridises and the excess probe washed off.