The insitu hybridization techniques is mainly use to detect a certain DNA or RNAsequences Jones, 2015.
These techniques utilize the probes to detect thesequences of DNA or RNA rather than using antibodies Jones, 2015. “In situ”is the detection of site where the DNA or RNA is located on the tissue sectionor cell Jones, 2015. In situ hybridization was first performed with aradioisotope-labelled probes then followed by autoradiography in the late 1960sCheng et al., 2017.
Then in 1980s, in situ hybridization were upgraded with theuse of direct labelled DNA probes with fluorophores that is complementary to a specificDNA sequences Cheng et al., 2017. Today, the latest in situ hybridizationtechniques are fluorescence in situ hybridization (FISH). FISH is an advancetechniques that have been greatly improved in terms of its resolution,specificity and sensitivity Cheng et al., 2017.
Cheng et al., (2017) stated that “FISHinvolves the use of fragments of DNA (probes) binding to interphase chromosomeof cytology specimens or paraffin embedded tissue sections”. Then, Mekki J.S.
,(2016) stated that “the use of FISH allowed the identification of both thestructural and numeric aberrations that specify certain hematopoietic andnon-hematopoietic malignancies”. The technique of FISH can be use on an air driedcytological preparation, FFPETS, frozen section, and fresh tissues, it candetect molecular abnormalities of either cancer or tumours, and it also can beuse in the detection of genetic and chromosomal numeric abnormalities Mekki,2016. In FISH, it mainly targeting thenuclear DNA of either the interphase cells or of the metaphase chromosomeaffixed to a microscope slide Bishop, 2010. The basic elements needed in FISHare target sequence and DNA probe Bishop, 2010. Before hybridization process,the DNA probe can be labelled either directly via the fluorophore or indirectlywith hapten (a small molecule that can only induce immune response whenattached a large carrier such as protein Shakoori, 2017) Bishop, 2010.After that, the labelled probe and the target DNA undergo denaturation to createa single-stranded DNA Bishop, 2010. The single stranded DNA of labelled probeand target DNA are then combined which allow the annealing process of complementaryDNA sequences Bishop, 2010. The indirectly labelled probe required an additionalstep for visualization of the non-fluorescent hapten that uses an enzymatic orimmunological detection system Bishop, 2010.
However, the probe that arelabelled directly can be evaluated directly by fluorescence microscopyBishop, 2010. Among theadvantages of FISH technique are it allowed the identification of a specificchromosome abnormalities, monitoring the progression of disease, and monitoringthe success of bone marrow transplantation Bishop,2010.The limitations of FISH are it cannot serve as a screening test for chromosomalrearrangements, can only detect known genetic aberrations, depend on combinedfluorochrome probes, and FISH analysis are restricted to the targetedchromosome or chromosomal sub-region Bishop,2010.