 FISH maps out single copy or repetitive DNA sequences through localization labeling of specific nucleic acids.The technique utilizes different DNA probes labeled with fluorescent tags that bind to one or more specific regions of the genome.Signals from the fluorescent tags can be seen with microscopy, and mutations can be seen by comparing these signals to healthy cells.For this to work, DNA must be denatured using heat or chemicals to break the hydrogen bonds; this allows hybridization to occur once two samples are mixed.