ISH and FISH

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In situ Hybridization (ISH) is a method that allows to localize and detect nucleic acid sequences within structurally intact cells or morphologically preserved tissues sections. Fluorescence in situ hybridization (FISH) is a kind of ISH which uses fluorescent probes binding parts of the chromosome to show a high degree of sequence complementarity. The basic principles for FISH and all other methods of in situ hybridization are the same, except one is utilizing a fluorescence probe to detect specific nucleotide sequences within cells and tissues. They differ from immunohistochemistry which usually localize proteins in tissue sections. In situ hybridization can be performed on a variety of targets, including RNA within cells, DNA in metaphase chromosome preparations obtained from mitotic cells, or DNA in interphase nuclei from cells in the non-mitotic phases of the cell cycle. In addition to the advantages of detection in morphologic context, in situ hybridization has become popular also because of its high sensitivity in nucleic acid detection. In situ hybridization has been widely used for research applications, including clinical cytogenetics, gene mapping, tumor biology and studies of chromosome evolution.