<< Back to glossary index


A genomic test where fluorescent probes are used to visualise the presence, absence and location of parts of the chromosomes.

Use in clinical context

In fluorescent in situ hybridisation (FISH), fluorescent probes (short stretches of DNA modified to fluoresce) are attached to particular stretches of DNA in the chromosomes. This process is known as hybridisation.

Hybridisation takes place due to normal DNA base-pairing ‘rules’, which allow the probe to reliably target a nucleotide sequence of interest. The chromosomes are then imaged using a microscope. The presence, absence or location of the fluorescence can be used to show when regions of chromosomes are missing (deletions), have extra copies (duplications) or have moved somewhere else in the genome entirely (translocations).

Last updated on 19th November, 2021