FISH is a technique that uses fluorescent probes that bind to only those regions of DNA or RNA that have nucleotide sequences complementary to the probe's sequence. It allows researchers to visualize chromosomes and specific genetic loci. There are several types of FISH probes including whole chromosome painting probes, repetitive sequence probes, and locus-specific probes. FISH has many diagnostic applications such as detecting chromosomal abnormalities, genetic translocations, and deletions associated with conditions like Prader-Willi syndrome.

1. FLUORESCENCE IN SITU
HYBRIDIZATION (FISH)
NAMA AHLI KUMPULAN
NUR ATIKAH AMIRA BINTI RANI
AHMAD AIMAN BIN ZAINAL
MOHD NABIL BIN ALI AKSAR
NOR SYAFINAS BINTI NOR ASHAAZLIM
RUZIANA BINTI YUSRI
YASMIN IZUREEN BINTI IBRAHIM

2. INTRODUCTION
• Used in detection of chromosomal abnormalities
• A technique in which single-stranded nucleic acids are interact so that
hybrids are formed by molecules with similar sequences.
• Enables us to assay multiple visualize localized signals in a single
specimen.
• Gives power to resolve several genetic elements / multiple gene
expression patterns through multicolor visual display.

3. FUNCTION
To help a researcher /
clinician identify where a
particular gene falls within an
individual’s chromosomes

4. TYPES OF FISH
Whole-
chromosome
painting probes
Repetitive
sequence
probes
Locus- specific
probes

5. WHOLE-CHROMOSOME PAINTING
PROBES
• Complex DNA probes derived from a single chromosome
• Most useful for clarifying chromosome rearrangements in metaphase
• Example :- genetic translocation in acute lymphoblastic leukaemia (ALL)
• Available for every human chromosome
• Led to development of two independent FISH techniques, multicolour FISH
(M-FISH) and spectral karyotyping (SKY)

7. REPETITIVE SEQUENCE
PROBES
• Hybridize to specific chromosomal regions
• Examples :- Pan-telometric probes (targeting the repeated TTAGGG sequences)
• Satellite DNA probes hybridize to multiple copies –resulting in a two very bright
fluorescent signals (metaphase & interphase)
• Suitable for detection of monosomy, trisomy etc. in both leukaemias and solid
tumors.

8. LOCUS-SPECIFIC PROBES
• To detect structural rearrangements,bind to gene of interest to
detect amplification and deletion.
• Using multi colour FISH , recurring translocations can be
identified
• Example :- BCR (breakpoint cluster region) gene at 22q11.2
detected at green fluorochrome
• BCR gene detected with green & 9q34 detected with red
fluorochrome will appear yellow spot in leukemia cell

10. PRINCIPLES
• Basic elements :- a DNA probe and a target sequence
• Before hybridization, the DNA probe is labeled by various means.
Two labeling strategies are commonly used :-
indirect labeling (left panel)
direct labeling (right panel)

11. PRINCIPLES
• The labeled probe and the target DNA are denatured
• Combining denatured probe and target allows the annealing of
complementary DNA sequences
• If the probe has been labeled indirectly, extra step is required for
visualization of the nonfluorescent hapten that uses an enzymatic
or immunological detection system.

13. CASE STUDY
• A 4-year-old girl who was referred to a laboratory to be investigated for clinical
obesity, mental deficiency and respiratory problems. The patient was born for
non-consanguineous and healthy biological parents. After normal pregnancy,
the patient was delivered by cesarean section at full term, with a birth weight of
2500 g, and the height and head circumference were unknown. In neonatal
stage, she presented severe hypotonia with feeding problems. Her
developmental progress was delayed. She walked and developed speech at
the age of 3 years, she presented severe dental problems. Methylation study
had confirmed the diagnosis, and for detecting etiology, fluorescence in situ
hybridization using probes for small nuclear ribonucleoprotein polypeptide N
(SNRPN) was necessary to confirm the deletion of paternal chromosome 15,
which is the predominant genetic defect in PWS.
Prader-Willi syndrome

14. DIAGNOSTIC APPLICATIONS OF FISH