FISH (Fluorescent In Situ Hybridization)
FISH is a molecular-cytogenetic technique that enables targeted testing of in advance selected chromosomes/genes. In our laboratory analysis by the FISH method is currently used for preimplantation genetic screening (PGS (PGT-A)) of selected chromosomes (usually for 5 the most common whole chromosomal aberrations) and for preimplantation genetic diagnosis/testing of unbalanced forms of familial rearrangements (PGT-SR) of a small extent where the NGS method cannot be applied.
Principle of the FISH method
Cell nuclei fixed to microscopic glass slide are analysed. The principle of the method is the labelling of several specific chromosomal regions by a fluorescently marked probe complementary to the DNA section concerned. The evaluation is performed by a fluorescence microscope. The method can be used to determine only numerical changes of selected chromosomes, their parts respectively, marked by a chosen fluorescence probe. When carrying out PGD (PGT-SR) to detect unbalanced forms of familial chromosomal rearrangement it involves a part of the chromosomes participating in this aberration. PGD (PGT-SR) using the FISH method usually precedes the chromosomal analysis of parents to verify the accuracy of the proposed combination of the fluorescence probes (so-called "set-up”).
Limitation of the FISH method
FISH cannot rule out any other diseases or foetal developmental defects not caused by a change in the number of diagnosed chromosomal regions.
Genetic analysis and consultation
2019/08/27 IVF Zentren Prof. Zech – Pilsen, RNDr. Martina Hrubá, Ph.D.