| Fluorescence in situ hybridization (FISH) techniques allow specific nucleic acid sequences to be ***ected in morphologically preserved chromosomes, cells or tissue sections. In combination with immunocytochemistry, Fluorescence in situ hybridization can relate microscopic topological information to gene activity at the DNA, mRNA, and protein level. FISH has become a molecular diagnostic technique utilizing fluorescently labeled DNA probes to ***ect or confirm gene or chromosome abnormalities. The sample DNA (metaphase chromosomes or interphase nuclei) is first denatured, a fluorescently labeled probe of interest is then added to the denatured sample mixture and hybridizes with the sample DNA at the target site as it re-anneals back into a double helix. The probe signal can then be seen through a fluorescent microscope and the sample DNA can be scored for the presence or absence of the signal. Unlike most other techniques used to study chromosomes, FISH does not have to be performed on cells that are actively dividing. This makes it a very versatile procedure. This technique is useful for identifying chromosomal abnormalities, gene mapping, characterizing somatic cell hybrids, identifying amplified genes and studying the mechanism of rearrangements. RNA ISH is used to measure and localize mRNAs and other transcripts within tissue sections or whole mounts. |
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