MSc zoology 7._TRANSGENIC_FISH_PRODUCTION.ppt

Science notes

1. TRANSGENIC FISH PRODUCTION

2. •An organism that has a foreign or modified gene transferred
to its genome using the in vitro genetic techniques is called a
genetically modified organism (GMO) or a transgenic
organism.
•Transgenes can originate from phylogenetically distant
organisms or from the same species.
• For the production of transgenic animal, a cloned gene is
transferred into the fertilized egg before the completion of
first cleavage.
•Scientists are seeking ways to genetically engineer fish and
other seafood species to introduce or amplify economically
valuable traits.
•Fish are of particular interest to researchers since many fish
produce large quantities of eggs; those eggs, being external to
the animal (as opposed to mammals that produce fewer eggs
internally), make it relatively simple to insert novel DNA

3. •Research on transgenic fish is currently under development
for at least 35 species of fish worldwide, as well as for a
variety of mollusks, crustaceans, plants, and marine
microorganisms, for various purposes.
•Transgenic technology has been successfully used to develop
fast-growing super-fish stocks for human consumption,
•to produce pharmaceuticals,
•to test water contamination in both developed and developing
countries.
•Several laboratories now have GM fish with increased growth
performance caused by extra copies of GH genes

4. A. Selection of species and genes
•For the aquacultural importance, Indian major carps,
Common carp, Channel catfish, Chinese carps,
Salmon, Trout and Tilapia are the best species for the
transgenic project.
• Improvement of growth rate, imparting disease and
environmental stress resistance are some important
traits for transgenesis.

5. B. Reporter genes
•Reporter gene is defined as a gene whose
products detects or marks the cells, tissues,
organisms that express the gene from those that
do not.
•Reporter genes isolated from prokaryotes, E. coli,
are used in fishes- lac Z gene, Cat
(Chloramphenicol Acetyl Transferase gene).
•Recently luciferase and green fluorescent protein
are used.
 

6. C. Genes of interest
1. Growth hormone gene
•Growth is a complex biological process involving genetic,
hormonal, nutritional and environmental factors.
• ‘Growth hormone’ (GH) is produced by the anterior lobe of
the pituitary plays the key role.
•It increases growth by stimulating appetite and improving the
food conversion efficiency.
•GH is a protein hormone having a molecular weight of about
22 kilodaltons.
•Transgenic fish carrying GH gene will produce growth
hormone endogenously by passing the necessity of exogenous
hormone treatment.
•GH gene has been cloned in some fishes either from the
genomic library or from the cDNA library.

7. 2. Antifreeze protein genes
•Production of cold resistant fish variety is useful for
establishing aquaculture industry in the temperate
region, where water gets frozen during winter.
•The gene responsible for imparting cold resistance was
cloned from winter flounder (Pseudopleuronectes
americanus), which lives in the polar sea.
•This species avoids freezing of its blood even at –7C
temperatures by producing a set of anti-freeze proteins
(AFP).
•AFP are produced in the liver and exported to the blood
stream.

8. 3. Disease resistance
•Fish has poorly developed antibody dependent
immunity.
•Efforts to produce disease resistance in fish stocks by
transgenesis have begun recently.
•The potential of Rainbow trout lysozyme gene as a
bacterial inhibitor was assessed in Atlantic salmon.

9. D. Techniques of gene transfer
1. Microinjection
•The most common method of gene transfer.
•Soon after fertilization the gene is microinjected into the
cytoplasm since the egg nucleus is not visible in the fishes.
•Linearised DNA rather than circular DNA is injected for the greater
probability of the former to get integrated into the host’s genome.
• Higher amount of DNA is used for cytoplasmic gene transfer than
when it is injected to the pronucleus.
• Some species has softer chorion such as catfish, Zebra fish.
•Small volume of the solution 1-2 nl of DNA containing >10
7
copies
should be injected.
• The rate of survival and integration of the transgene after
microinjection varies widely in different species of fishes and in
different batches of the same species.
 

10. 2. Electroporation
•It utilizes a series of short electrical pulses to make the
membrane porous and permeable to DNA
incorporation.
•Embryos and sperms can be electroporated.
•It is less labour intensive and does not require special
expertise for gene transfer as needed in the case of
microinjection.
• It is easier to do this in spermatozoa than in embryos,
which possess tough chorion.
•The gene transfer efficiency and integration rate do not
differ much between electroporation and
microinjection methods.
•In zebra fish 0.1 milli second pulses of 125/cm for
batches of 200 eggs.

11. E. Detection of transgene
•There are various ways and means to detect
this.
•Most of them used southern blot and
northern blot to detect the transgenes using
a suitable probe (dot blot).

12. Glofish
•The GloFish is a patented brand of genetically
modified (GM) fluorescent zebrafish with bright red,
green, and orange fluorescent color.
•The transgenic zebrafish (Danio rerio) expressing a
red fluorescent protein from a sea anemone under
the transcriptional control of the promoter from the
myosin light peptide 2 gene of zebrafish.

13. Food safety of transgenic (GM) fish
•GM food safety depends on the nature of the
gene, the transgene product it encodes and the
resulting phenotype.
•Ethics and animal protection concerns allows the
development of healthy and safe fish only.
•Transgenic fish have received extra copies of GH
genes, resulting in only moderately raised levels
of circulating GH.
•GH is a protein hormone which is degraded along
with all other food protein.

14. •Meat from fish modified with GH is regarded as
completely safe for human consumption
Concerns have been voiced of the possible risks of
consumption of transgenes,
•their resulting protein,
•potential production of toxins by aquatic transgenic
organisms,
•changes in the nutritional composition of foods,
•activation of viral sequences and
• allergenicity of transgenic products

15. Environmental impact of transgenic fish
•The possible impacts from the escape of GM organisms
from aquaculture facilities are of great concern to
some scientists and environmental groups.
•Critics and scientists predict that GM fish could breed
with wild populations of the same species and
potentially spread undesirable genes
•Escaped transgenic fish could harm wild fish through
increased competition or predation.
•The consequences of such competition would depend
on many factors, including the size of the wild
population, the number and specific genetic strain of
the escaped fish, and local environmental conditions.

16. •FDA could require that only sterile GM fish be
approved for culture in ocean pens.
•Fertilized fish eggs that are subjected to a heat or
pressure shock retain an extra set of chromosomes.
•The resulting triploid fish do not produce normal
eggs or sperm, and females do not exhibit
maturation of the ovary or reproductive behaviors.
•Thus, all-female lines of triploid fish are the best
current method to ensure non-breeding populations
of GM fish.

17. Possible Benefits and Disadvantages of GM Fish and
Seafood
•Biotechnology proponents maintain that genetic
modification has many advantages over traditional
breeding methods, including faster and more specific
improvement of beneficial traits.
•Genetic modification allows scientists to precisely
select traits for alteration, enabling them to create an
organism that, for example, grows larger or faster or
has a different nutritional content.
•Increased freeze resistance in fish could lead to the
ability to grow freeze-resistant species in previously
inhospitable environments, allowing aquaculture to
expand into previously unsuitable areas.

18. •Biotechnology proponents claim these advantages
could translate into a number of potential benefits,
such as reduced costs to producers, lower prices for
consumers for edible fish and pharmaceuticals, and
environmental benefits, such as reduced water
pollution from wastes.
•M.ajority of consumers in the United States appear
to have accepted GM food and feed crops, it is
uncertain whether consumers will be as accepting of
GM fish

19. Conclusion
•The future success and application of transgenic fish
will depend upon by successful demonstration of a
lack or potential lack of environmental risk, food
safety, appropriate government regulation and
labeling, public education and development of
genetic sterilization for transgenic fish.
• Appropriate, well executed public education may be
necessary to gain broad consumer acceptance of
transgenic fish from an environmental standpoint
and perhaps in relationship to how “organic” a
transgenic fish may be.

20. Thank you