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.

1. ALLOZYMES AND ISOZYMES
Mohit Kumar Ram and Jitendra Kumar
COF, Mangalore
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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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8. Genetics
A
a
A’
a’
Alleles
Alleles
A
a
A’
Gene-A
a’
Gene-B
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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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14. Electrophoresis
Allozyme electrophoresis System
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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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20. RFERENCES
• www.google.com/www.wikipedia.com/isoenz
ymes
• www.google.com/www.wikipedia.com/allozy
mes
• www.google.com/pdf/file/genetics in fisheries
• www.google.com/pdf/file/application of
isoenzymes and allozymes in fisheries
• www.google.com/pdf/file/allozyme
electrophoresis in fisheries
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21. THANK YOU
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