What is the principle of Fluorescence in situ hybridization (FISH) method?

The core principle involved in FISH involves pairing the nuclear DNA (either from metaphase chromosomes or interphase cells) on a microscope slide, with a nucleic acid probe. These probes can be labeled directly by integrating a fluorophore or indirectly using a hapten. The labeled probe and target DNA are denatured before being combined to allow complementary DNA sequences to anneal. The labeled probe and target DNA are denatured before being combined to allow complementary DNA sequences to anneal. If the probe is indirectly labeled, an extra step is needed for visualization using an enzymatic or immunological detection system. Subsequently, fluorescence microscopy is used to assess the signals. The immunological detection system relies on the binding of antibodies to specific antigens and the enzymatic detection system utilizes fluorochromes.