Fig. 1 Flow chart of a typical
FISH. The procedure includes
the following steps: (1) fixation
of the specimen directly in
sample tubes; (2) transfer of the
sample on a glass slide and
preparation of the sample, in-
cluding specific pretreatment
steps; (3) hybridization with the
respective probes for detecting
the respective target sequences;
(4) washing steps to remove
unbound probes; (5) mounting,
visualization and documentation
of results
Fig. 2 Direct (a, b) and indirect (c – e) labelling of probes using a
reporter molecule like digoxygenin (DIG) that is then detected by
fluorescent antibody, horseradish peroxidase (HRP) that used fluores-
cein – tyramide as substrate for the enzymatic signal amplification
[tyramide signal amplification (TSA)], or with the combined use of
polyribonucleotide probes, internally labelled with digoxygenin, with
the tyramide signal amplification systems