An opportunity to look inside of the individual cell for the direct visualizationin situof “what happened?” is the most wonderful feature offered by fluorescencein situhybridization (FISH). DNAin situhybridization is a technique that allows the visualization of defined sequences of nucleic acids within the individual cells. The method is based on the site specific annealing (hybridization) of single-stranded labeled DNA fragments (probes) to denatured, homologous sequences (targets) on cytological preparations, like metaphase chromosomes, interphase nuclei, or naked chromatin fibers. Visualization of hybridization sites becomes possible after detection steps by using a wide spectrum of the fluorescent dyes available.
