The document discusses allozymes and isozymes, which are genetic markers used in ichthyotaxonomy to study phylogenetic relationships between fish species. Allozymes represent enzymes catalyzed by different alleles of the same gene, while isozymes are enzymes from different genes that catalyze the same reaction. Allozyme electrophoresis is used to detect genetic variation at the enzyme level by identifying different allozyme forms. While allozymes and isozymes provide useful information and are easy to use, they have limitations as only a small fraction of enzyme loci are polymorphic and a limited number can be analyzed.
2. OUTLINE
Introduction
Allozymes
Isozymes
Use of Allozymes & Isozymes
Significance of Allozymes & Isozymes study, in Ichthyotaxonomy
Allozyme electrophoresis
Advantages & disadvantages
Conclusion
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3. Introduction
In Ichthyotaxonomy, DNA based molecular marker(Genetic
Marker) plays an important role to identify the phylogenic
trends of evolution
Now a days it is being replaced by various other methods of
DNA-marker like,
-Nuclear DNA markers(nDNA)
-Mitochondrial DNA markers(mtDNA)
-Restriction fragment length polymorphism (RFLP) etc.
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4. Molecular Marker
It is typical type of DNA sequence
Used to mark a particular or specific location
on the chromosomes
It may also called genetic marker
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5. Types of Molecular Marker
Allozyme markers
Nuclear DNA markers (nDNA)
Mitochondrial DNA markers (mtDNA)
Restriction fragment length polymorphism (RFLP)
Random amplified polymorphic DNA (RAPD)
Amplified fragment length polymorphism (AFLP)
Tandem repeated DNA (mini and microsatellites)
Single nucleotide polymorphism (SNP)
Expressed sequence tags (ESTs)
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6. Basic functions of all markers
Genetic identification of aquaculture stocks
Identify the phylogenetic relationship between the different species of fishes
Monitoring of inbreeding or other changes in the genetic composition of the
stocks
events and genetic drift
Comparisons between hatchery and wild stocks
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7. Isoenzymes & Allozymes
• Isoenzymes & Allozymes were first discovered by
R.L.Hunter & Clement Markert in 1957
• Now days the two words i.e. Isoenzymes & Allozymes
are usually used interchangeably
• ExamplesLactate dehydrogenase (LDH) (chr-12) & (chr-15),
malate dehydrogenes glucosephosphate, glucokinase etc.
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9. Allozyme
It represents the enzymes which is catalyzed by the
different alleles of the same gene
Allozyme
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10. Isozyme/Isoenzyme
• It represent the enzymes from different genes that
process or catalyzed the same reaction
• Differs in amino acid sequence
E1
A + B
E2
AB
…..then E1 & E2 will be Isoenzymes
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11. Functions of Allozymes in fisheries
To study the Genetic Variability of stock
To demonstrate Allozyme electrophoresis
To identify the genetic behavior of smolt age
To study the genetic characterization of the species and stock
To study the genetic drift of the species and stock
Genome mapping
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12. Functions of Allozymes in
Ichthyotaxonomy
Individual identification
Mixed Stock Fishery Analysis(MSFA)
To identify the phylogenetic relationship between the
different species of fishes
To identify and arrangement of the species and stock on
the basis of their genetic affinity
To identify the genetic diversity with in the stock &
cultured species
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13. Allozyme electrophoresis
• Allozyme electrophoresis denotes technique for
identifying genetic variation at the level of enzyme
• Genetically different forms of an enzyme that are
produced by different alleles at locus
• Detected by electrophoresis
• It is a Co-Dominant Mendelian characters
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15. Protein Pattern after electrophoresis
Protein Pattern after electrophoresis
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16. Process of electrophoresis
Extraction , electrophoresis and observation of protein
bands are the methods for detection of allozyme
variation
Generally starch gel used for staining
40-50 individual can be analyzed per gel
Drawback of this is that only small fraction of enzyme
loci
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17. Advantages of Allozymes &
Isoenzymes
Co dominant type markers
Easy to use
Easily adjustable from species to species
Low cost
General applicability
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18. Disadvantages of Allozymes &
Isoenzymes
Limited number of available Allozyme loci precludes
their use in large-scale genome mapping
Heterozygote deficiencies due to null alleles
Reduce the level of detectable variation due to some
changes in DNA sequence
Only a small fraction of enzyme loci appear to be
allozymically polymorphic
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19. CONCLUSION
• Although, Isoenzyme & Allozyme are not used so
much but yet it gives satisfactory result
• It should apply to the genetics of phylogeny as it
gives good result
• It has limited use in fisheries sciences rather than
other sciences
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