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LUCKNOW UNIVERSITY
INTERNAL ASSESSMNT
ISABELLATHOBURN COLLOEGE
DEPARTMENT OF ZOOLOGY
TOPIC- MICRONUCLIETEST IN FISHES
Aditi bajpai
M.sc sem 4th
2210384310002
z/22/40
Contents
Micronuclei test
What are micronuclei?
Formation of micronucleus
MN Induction
Micronucleus assay with fluorescence in situ hybridization
(MNA,FISH)
Suitability of MN assay in fish
Conclusion
Micronuclei test
• The micronucleus test is a method used to assess the
genotoxicity in fishes.
• It was developed by Schmid, 1975 and Heddle, 1973.
• MNT is a short time screening method used widely to
detect genotoxic effects.
• It is one of the simplest, reliable, least expensive and rapid
screening system for both clastogenic ( chromosomal
fragments and formation of acentric fragments) and
aneugenic ( chromosomal loss) events.
• MN test is well established for mutagenicity screening in
several systems such as ovary, bone
marrow, epithelial tissues, peripheral blood,
liver, exfoliated buccal cells and foetus cells of several
laboratory animals and humans.
• Frogs, birds and fishes are widely investigated by micronucleus
test to detect the environmental pollution leading to genotoxic
damage.
What is micronucleus?
• MICRONUCLEI: are extranuclear small bodies,
resembling interface nucleus in structure,
formed in dividing cells.
• Micronuclei formation can occur in any dividing
cell of any tissues in any species as shown by
the values of Micro nucleated
Erythrocytes (MNE).
• Schroder, 1966, studied first the formation
of micronuclei in mammalian bone marrow cells.
• The MN are also known as Howell-jolly-bodies.
• MN contains either acentric chromosomal
fragments or whole chromosome.
Formation of micronucleus
• During meiosis, Acentric chromosomal
fragments or whole chromosome that
are unable to travel to spindle poles and
are thus, not included in either daughter
nucleus, give rise to micronucleus.
• At telophase, a nuclear envelope forms
around the lagging chromosomal fragm
ent and it resembles a interphase nucleus
.
MN induction: sensitive biomarker for
genotoxicity
• An enhanced frequency of cells with MN is
reliable biomarker for genotoxicological
manifestations in organisms.
• This happens due to the exposure of a
Clastogenic or aneugenic agent.
• Exposure to clastogenic or aneugenic agents
results in increased number of cells with MN,
which is a suitable biomarker for
genotoxicological manifestation.
Routes for the formation or induction of MN
• There are two major routes for the formation or induction of MN
A. MN having chromosomal fragments are formed-
• Direct DNA damage
• Replication on a damaged DNA template.
• Inhibition of DNA synthesis.
B. MN having whole chromosomes are mainly formed from-
• Failure of the mitotic spindle, kinetochore or other parts of the
mitotic apparatus or by,
• By alternations in cellular physiology and mechanical disruptions.
Micronucleus assay with fluorescence in situ
hybridization (MNA, FISH)
• FISH is a versatile technique.
• It consists of labelling of centromeric region of the
chromosomes with a probe in the presence of Cytochalasin-
B ( an indicator of actins).
• Due to labelling, it becomes possible to-
1. Differentiate between MN whole chromosome(
Centromere positive MN) and an acentric chromosomal
fragments (centromere negative micronucleus).
2. The presence of cytochalasin B ensures that cells
containing MN are an outcome of in-vivo rather than ex-
vivo division.
Suitability of MN assay in Fish
• Fish chromosomes are usually smaller in size and greater in number.
• Since, teleost erythrocytes are nucleated, MN can be easily scored in them due to
clastogenic activity.
• MN formation depends on the rate of proliferation of cells, which in turn depends
on fish species and their target tissues coupled with environmental stressors,
pollutants, etc.
• As fish occupy different trophic levels, it react to even low concentration of
pollutants, they are regarded as good indicators of health aquatic ecosystems.
• MNT is one of the most useful biomarkers to evaluate genetic damage.
Conclusion
• The micronucleus test is a method used to assess the genotoxicity in fishes.
• MICRONUCLEI: are extranuclear small bodies, resembling interface nucleus
in structure, formed in dividing cells.
• MN test is well established for mutagenicity screening in several systems
such as ovary, bone marrow, epithelial tissues, peripheral blood,
liver, exfoliated buccal cells and foetus cells of several laboratory animals
and humans.
Bibliography
• Bolognesi, Claudia, et al. “Genotoxicity biomarkers in the assessment of heavy metal
effects in aquatic ecosystems: an overview.”AquaticToxicology 98.1 (2010): 1-6.
• Kumar,Ashok, et al. “Micronucleus assay in fish: A bio-monitoring tool for aquatic
pollution.” Environmental Monitoring and Assessment 188.8 (2016): 459.
• Pal, Sagar, et al. “Micronucleus test in fish: a practical approach.” Mutagenesis 27.2 (2012):
177-183.
• Bhattacharya, Sarita, et al. “Micronucleus test: a useful assay for monitoring genotoxic
effects of heavy metals in Oreochromis mossambicus.” EnvironmentalToxicology and
Pharmacology 32.1 (2011): 66-74.
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2441751/

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Micronuclei test.M.sc.zoology.fisheries.

  • 1. LUCKNOW UNIVERSITY INTERNAL ASSESSMNT ISABELLATHOBURN COLLOEGE DEPARTMENT OF ZOOLOGY TOPIC- MICRONUCLIETEST IN FISHES Aditi bajpai M.sc sem 4th 2210384310002 z/22/40
  • 2. Contents Micronuclei test What are micronuclei? Formation of micronucleus MN Induction Micronucleus assay with fluorescence in situ hybridization (MNA,FISH) Suitability of MN assay in fish Conclusion
  • 3. Micronuclei test • The micronucleus test is a method used to assess the genotoxicity in fishes. • It was developed by Schmid, 1975 and Heddle, 1973. • MNT is a short time screening method used widely to detect genotoxic effects. • It is one of the simplest, reliable, least expensive and rapid screening system for both clastogenic ( chromosomal fragments and formation of acentric fragments) and aneugenic ( chromosomal loss) events. • MN test is well established for mutagenicity screening in several systems such as ovary, bone marrow, epithelial tissues, peripheral blood, liver, exfoliated buccal cells and foetus cells of several laboratory animals and humans. • Frogs, birds and fishes are widely investigated by micronucleus test to detect the environmental pollution leading to genotoxic damage.
  • 4. What is micronucleus? • MICRONUCLEI: are extranuclear small bodies, resembling interface nucleus in structure, formed in dividing cells. • Micronuclei formation can occur in any dividing cell of any tissues in any species as shown by the values of Micro nucleated Erythrocytes (MNE). • Schroder, 1966, studied first the formation of micronuclei in mammalian bone marrow cells. • The MN are also known as Howell-jolly-bodies. • MN contains either acentric chromosomal fragments or whole chromosome.
  • 5. Formation of micronucleus • During meiosis, Acentric chromosomal fragments or whole chromosome that are unable to travel to spindle poles and are thus, not included in either daughter nucleus, give rise to micronucleus. • At telophase, a nuclear envelope forms around the lagging chromosomal fragm ent and it resembles a interphase nucleus .
  • 6. MN induction: sensitive biomarker for genotoxicity • An enhanced frequency of cells with MN is reliable biomarker for genotoxicological manifestations in organisms. • This happens due to the exposure of a Clastogenic or aneugenic agent. • Exposure to clastogenic or aneugenic agents results in increased number of cells with MN, which is a suitable biomarker for genotoxicological manifestation.
  • 7. Routes for the formation or induction of MN • There are two major routes for the formation or induction of MN A. MN having chromosomal fragments are formed- • Direct DNA damage • Replication on a damaged DNA template. • Inhibition of DNA synthesis. B. MN having whole chromosomes are mainly formed from- • Failure of the mitotic spindle, kinetochore or other parts of the mitotic apparatus or by, • By alternations in cellular physiology and mechanical disruptions.
  • 8. Micronucleus assay with fluorescence in situ hybridization (MNA, FISH) • FISH is a versatile technique. • It consists of labelling of centromeric region of the chromosomes with a probe in the presence of Cytochalasin- B ( an indicator of actins). • Due to labelling, it becomes possible to- 1. Differentiate between MN whole chromosome( Centromere positive MN) and an acentric chromosomal fragments (centromere negative micronucleus). 2. The presence of cytochalasin B ensures that cells containing MN are an outcome of in-vivo rather than ex- vivo division.
  • 9. Suitability of MN assay in Fish • Fish chromosomes are usually smaller in size and greater in number. • Since, teleost erythrocytes are nucleated, MN can be easily scored in them due to clastogenic activity. • MN formation depends on the rate of proliferation of cells, which in turn depends on fish species and their target tissues coupled with environmental stressors, pollutants, etc. • As fish occupy different trophic levels, it react to even low concentration of pollutants, they are regarded as good indicators of health aquatic ecosystems. • MNT is one of the most useful biomarkers to evaluate genetic damage.
  • 10. Conclusion • The micronucleus test is a method used to assess the genotoxicity in fishes. • MICRONUCLEI: are extranuclear small bodies, resembling interface nucleus in structure, formed in dividing cells. • MN test is well established for mutagenicity screening in several systems such as ovary, bone marrow, epithelial tissues, peripheral blood, liver, exfoliated buccal cells and foetus cells of several laboratory animals and humans.
  • 11. Bibliography • Bolognesi, Claudia, et al. “Genotoxicity biomarkers in the assessment of heavy metal effects in aquatic ecosystems: an overview.”AquaticToxicology 98.1 (2010): 1-6. • Kumar,Ashok, et al. “Micronucleus assay in fish: A bio-monitoring tool for aquatic pollution.” Environmental Monitoring and Assessment 188.8 (2016): 459. • Pal, Sagar, et al. “Micronucleus test in fish: a practical approach.” Mutagenesis 27.2 (2012): 177-183. • Bhattacharya, Sarita, et al. “Micronucleus test: a useful assay for monitoring genotoxic effects of heavy metals in Oreochromis mossambicus.” EnvironmentalToxicology and Pharmacology 32.1 (2011): 66-74. • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2441751/