Final answer:
In DNA fingerprinting, a DNA probe used is complementary to the target sequence and is tagged with a radioactive atom or fluorescent dye for visualization.
Step-by-step explanation:
In DNA fingerprinting, the DNA probe that is used is complementary to the DNA sequence of the repeats. This means that the nucleotide bases of the probe will pair up with the bases of the target DNA sequence following the base-pairing rules (adenine with thymine, and cytosine with guanine). The probe, which is a short piece of DNA, is typically labeled or tagged with a molecular beacon such as a radioactive phosphorus atom or a fluorescent dye, enabling the visualization of the DNA fragments to which the probe hybridizes after it has annealed to the corresponding complementary DNA sequence in the sample.
This process is crucial in identifying matching DNA sequences in different samples, which is the essence of DNA fingerprinting. The probe is carefully designed to only bind to a specific sequence related to the gene or the sequence of interest. This allows for the detection of DNA from cells that contained recombinant plasmids or to screen for a gene within a genomic library.
The method of using labeled DNA probes is invaluable in a variety of applications, including medical diagnosis and forensic investigations, where identifying precise genetic sequences is critical.