Manipulation techniques for chromosome set manipulation

1. Chromosomal Set Manipulation
for Better Aquaculture
Mr. Mangesh M. Bhosale, R.R.Mugale,
S.R. Surnar, H.. Vardia and Hinnananda,
B.R.
College of Fisheries, Kawardha (C.G.)
College of Fisheries, Ratnagiri

2. The changes in the number of chromosome
sets by destruction of one set, during
karyokinesis.

3. METHODS OF CHROMOSOME MANIPULATION
1) Inactivation of gametes
• Irradiation of spermatozoa with gamma radiation,
X-ray or U-V light or dimethylsulphate destroys
the genetic material without inactivating the
spermatozoa.
• UV irradiation form pyrimidine dimers in DNA
leading to its genetic inactivation.
• The optimum dose of UV varies with
spermatozoa concentration.

4. • Shock treatment (to prevent second polar body
release), and establishes XX condition.
• To induce androgenesis, the maternal (egg)
genome is inactivated by irradiation and fertilized
with normal sperm.

5. 2) Shock treatment
• Manipulation is done by application of thermal or
temperature (cold and heat), pressure or chemical
shock.

6. THERMAL SHOCK
• Cold shocks for cold water species (salmonids) - 0°C
• Cold shocks for warm water species (Common carp,
Tilapia and Indian major carps), 8-12°C.
• Heat shock for cold water fishes around
26-28°C.
• Heat shock for warm water fishes 39-42°C.

7. PRESSURE SHOCK
• Simple to administer.
• Pressure range varies between 7000 to
9000 pascals (Psi).
• Less side effect than the thermal shock.

8. CHEMICAL SHOCK
• Colchicine and cytochalasin-b disrupt cell
division and induce ploidy induction.
• Anaesthetics such as Nitrous Oxide and
Freon 22 induce triploidy.
• But the results are inconsistent and
unsatisfactory.

9. DETECTION OF POLYPLOID INDIVIDUALS
i) Chromosome analysis
-Simplest, appropriate method for
determining the ploidy level.
- Very much labour intensive , time
consuming.

10. • ii) This can be done with the help of light
microscopy.
• iii) Flow cytometry is used to estimate the
DNA concentration of diploid and triploids.

11. 1. ANDROGENESIS
• Results in all-paternal inheritance.
• Method requires the suppression of the first
mitotic cleavage.

12. 2.GYNOGENESIS
• It is a reproductive manipulation resulting
in all-maternal inheritance.

13. APPLICATION OF GYNOGENESIS
• In female homogametic species all female
population is produced.
• 50 to 100% inbred individuals can be
produced in a single generation.
• Inbred lines of fish can be crossed to
produce hybrid vigour or heterosis.
• It has the ability to map genes relative to
their centromeres in fish after retention of
the second polar body.

14. POLYPLOIDY
• Polyploidy is the induction of individuals
with extra (triploids, tetraploids) sets of
chromosomes.

15. TRIPLOIDY
• They are sterile and therefore useful for
stocking natural bodies of water where
population control is desirable.
• They grow faster at and after sexual
maturity (in triploids 20-30% of the energy
utilized for normal gonadal development is
diverted to somatic growth).

16. TETRAPLOIDS
• Induction of tetraploidy involves applying
shock treatment soon after zygote
formation.
• This is to prevent the first mitotic cleavage
thereby inducing the tetraploid condition.
• Unlike triploids, tetraploids reach sexual
maturity.

17. References
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19. THANK YOU