fish in diagnostics
TRANSCRIPT
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o A powerful cytogenetic technique.
o It is used to detect localize the presence
or absence of specific DNA sequences on
chromosomes.
o Exploits the ability of single stranded
DNA to anneal to complementary DNA.
o Uses fluorescent probes.
o Fluorescence microscopy detects the
presence of fluorescent probes.
o It is a powerful technique used in the
detection of chromosomal abnormalities.
Fluorescence in situ hybridization (FISH) is a molecular
diagnostic technique utilizing labeled DNA probes to
detect or confirm gene or chromosome abnormalities.
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FISH Targets
- Metaphase Chromosomes
- Interphase Nuclei
- Fixed Tissues
- Cells in culture
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I t i s a r el at i vel y new cyt ogenet i c t echni que t hat al l ows a cyt ogenet i ci st t o det er mi ne how many copi es of a par t i cul ar chr omosome ar e pr esent wi t hout havi ng t o go t hr ough al l of t he st eps i nvol ved i n pr oduci ng a kar yot ype.For example,
FISH analysis can quickly tell you how many number 21 chromosomes
are present, but it cannot tell you anything about the structure of those
chromosomes.
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How does FISH work?FISH is useful to help to identify where a particular gene
falls within an individual's chromosome.
A. The first step is to prepare short sequences of single-stranded
DNA that match a portion of the gene. These are called probes.
B. The next step is to label these probes by attaching one of a
number of colors of fluorescent dye.
C. DNA is composed of two strands of complementary molecules
that bind to each other like chemical magnets.
D. When a probe binds to a chromosome, its fluorescent tag
provides a way to see its location using fluorescent microscope.
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General schematic diagram of FISH
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Dire
ct a
nd
ind
irec
t lab
ellin
go
f pro
bes
DIRECT
FITC; rhodamine;Texas
red;cy2;cy3;cy5 and AMCA dyes
are most frequently used
INDIRECT
biotin;digoxigenin & DNP reprtr
molecules are frequently used
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Tagging of probes by nick translation
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Types of Probes
Locus specific probes bind to a
particular region of a chromosome.
This type of probe is useful when
scientists have isolated a small
portion of a gene and want to
determine on which chromosome
the gene is located.
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Alphoid or centromeric repeat
probes are generated from
repetitive sequences found in
the middle of each
chromosome. Researchers use
these probes to determine
whether an individual has the
correct number of
chromosomes. These probes
can also be used in combination
with "locus specific probes" to
determine whether an individual
is missing genetic material from
a particular chromosome.
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Whole chromosome
probes are actually collections
of smaller probes, each of
which binds to a different
sequence along the length of a
given chromosome. Using
multiple probes labeled with a
mixture of different fluorescent
dyes, scientists are able to
label each chromosome in its
own unique color. The resulting
full-color map of the
chromosome is known as a
spectral karyotype. Whole
chromosome probes are
particularly useful for
examining chromosomal
abnormalities, for example,
when a piece of one
chromosome is attached to the
end of another chromosome.
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Chronic myeloid leukemia
• Cancer of White Blood Cells.
• Increased and unregulated groth of myeloid cells in
bone marow and accumulation of these cells in blood.
• It is a type of first malignancy to be linked to a clear
genetic abnormality which is the chromosomal
translocation known as philadelphia chromosome.
• More common in males.
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Philadelphia chromosome
• In this translocation,
parts of chromosomes
9th and 22nd switch
places.
• As a result , part of
BCR gene from
chromosome 22 is
fused with ABL gene
on chromosome.
• BCR ABL fusion gene
prouct is a tyrosine
kinase-remains
continuously on.
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• Green fluorescence – BCR gene
• Red fluorescence - ABL gene
• Yellow fluorescence – BCR ABL
fusion gene
Interphase FISH on a nucleus using an
Exta-signal probe to detect
the BCR/ABL translocation.The green
signal indicates the presence of
the BCR gene, red signals indicate the
presence of the ABL gene and the red-
green fusion (yellow) signal confirms a
BCR/ABL translocation. The extra red
signal confirms this is not a false positive
result.
METAPHASE FISH
INTERPHASE FISH
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Genetic diseases identified using FISH
Prader-Willi SyndromePrader-Willi syndrome is a complex genetic condition that affects many parts of the body. In infancy, this condition is characterized by weak muscle tone (hypotonia), feeding difficulties, poor growth, and delayed development. Beginning in childhood, affected individuals develop an insatiable appetite, which leads to chronic overeating (hyperphagia) and obesity. Some people with Prader-Willi syndrome, particularly those with obesity, also develop type 2 diabetes mellitus (the most common form of diabetes).
Prader-Willi syndrome is caused by the loss of function of genes in a particular region
of chromosome 15.
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Angelman SyndromeAngelman syndrome is a complex genetic disorder that primarily affects the nervous system. Characteristic features of this condition include delayed development, intellectual disability, severe speech impairment, and problems with movement and balance.
DiGeorge and velo-cardio-facial Syndromes
It is caused by deletion of small piece of
long arm of chromosome 22 near the
middle at a location designated as
22q11.2
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Deletion detected by FISH
Deleted region of
chromosome 22-no flourescnt
signal
intact chromosome 22 giving a fluorescent
signal
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• Miller-Dieker Syndrome
• Williams Syndrome de Williams
• Wolf-Hirschhorn Syndrome
• Smith-Magenis Syndrome
• Kallmann Syndrome etc. are the other methods.
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Applications of FISH DiagnosticsFISH is often used in clinical studies : If a patient is infected
with a suspected pathogen, bacteria, from the
patient's tissues or fluids, are typically grown on agar
to determine the identity of the pathogen. Many
bacteria, however, even well-known species, do not
grow well under laboratory conditions.
FISH can be used to detect directly the presence of
the suspect on small samples of patient's tissue.
FISH can also be used to compare the genomes of
two biological species, to
deduce evolutionary relationships.
FISH is widely used in the field of microbial ecology,
to identify microorganisms.
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Often parents of children with a developmental
disability want to know more about their child's
conditions before choosing to have another
child. These concerns can be addressed by
analysis of the parents' and child's DNA. In
cases where the child's developmental disability
is not understood, the cause of it can potentially
be determined using FISH
and cytogenetic techniques.
In medicine, FISH can be used to form
a diagnosis, to evaluate prognosis, or to
evaluate remission of a disease, such
as cancer.
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o FISH is performed on a variety of specimen types such as blood, bone
marrow and paraffin-embedded tissue sections.
o Because of the higher sensitivity, FISH testing can detect mosaicism for
clonal chromosome changes,and is therefore useful in the detection of
minimal residual disease following treatment (e.g., interferon for chronic
myelogenous leukemia [CML]).
o Because the majority of specific deletions are sub-microscopic and can
only be detected by molecular tests, FISH plays a critical role in the
confirmation of microdeletion syndromes.
o FISH is also useful in solid tumors. For example, in determining the
prognostic role of HER-2/neu gene amplification or overexpression in
breast cancer.
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Presented by :
Name : ANJALI BAJAJ
Roll No :1754