Fluorescence in situ hybridization

Fluorescence in situ hybridization (FISH) detects specific DNA or RNA sequences inside cells using fluorescently labeled nucleic-acid probes that bind matching sequences.

Nucleic acid hybridization: The pairing of complementary nucleic-acid strands through specific base interactions. FISH relies on complementary probe sequences binding their targets in fixed cells.
Chromosome painting: A cytogenetic technique that labels entire chromosomes or chromosome regions with fluorescent probes. This FISH application reveals chromosome identity and large-scale rearrangements.
DNA: The molecule that stores hereditary information in most organisms, usually as two complementary nucleotide strands. DNA is the principal target in chromosome and gene-focused FISH assays.
Polymerase chain reaction: A laboratory method that amplifies selected DNA sequences through repeated cycles of heating and enzymatic synthesis. PCR amplifies DNA, whereas FISH shows where target sequences occur in cells.
Fluorescent probe: A molecule labeled with a fluorophore that emits light after excitation and can mark a chosen target. FISH probes carry fluorescent labels that make bound target sequences visible.
Comparative genomic hybridization: A method that compares DNA copy number across genomes using differentially labeled sample and reference DNA. Its array-based form extends FISH principles to genome-wide copy-number analysis.
RNA: A class of nucleic acids involved in gene expression, regulation, and other cellular functions. RNA-targeted FISH can reveal transcript location and abundance inside cells.
Immunofluorescence: A technique that uses fluorescently labeled antibodies to detect proteins in cells or tissues. It detects proteins through antibody binding rather than nucleic-acid hybridization.
Fluorophore: An atom or molecule that absorbs light at one wavelength and emits light at a longer wavelength. Fluorophores attached to probes generate the signal recorded in FISH images.
HER2/neu: A gene encoding a receptor tyrosine kinase whose amplification can drive some breast and other cancers. FISH can measure HER2 gene amplification to help classify tumors and guide treatment.

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