Modern genetics

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Transgenic Organisms
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Transgenic Organisms
The Transgenism is one of the thrust areas of
Biotechnology /Genetic Engineering. The methods
of gene transfer lead to the production of
Transgenic animals and plants. These Transgenic
organisms are called Genetically Modified
Organisms.
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Transgenic animal is one that carries a foreign
gene that has been deliberately inserted into its
genome. The foreign gene is constructed using
recombinant DNA methodology. In addition to a
structural gene, the DNA usually includes other
sequences to enable it to be incorporated into
the DNA of the host and to be expressed
correctly by the cells of the host.
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Transgenic sheep and goats have been produced
that express foreign proteins in their milk.
Transgenic chickens are now able to synthesize
human proteins in the "white" of the
eggs. Transgenic mice have provided the tools for
exploring many biological questions
Normal mice cannot be infected with polio virus.
They lack the cell-surface molecule that, in
humans, serves as the receptor for the virus. So
normal mice cannot serve as an inexpensive,
easily-manipulated model for studying the
disease. However, transgenic mice expressing
the human gene for the polio virus receptor can
be infected by polio virus and even develop
paralysis and other pathological changes
characteristic of the disease in humans
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Transfection Molecular farming
The uptake of genes by the cells in animals is
called transfection. The transfected cells are
used for a variety of purposes production of
transgenic animals of commercial value.
production of chemicals and pharmaceutical
drugs. study of structure and function of genes.
The production of Transgenic animals of
commercial value such as livestock animals and
fishes is called as Molecular farming.
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Gene transfer methods
In transfection, fertilized eggs / embryos or the
cultured cells are employed. The Embryonic Stem
Cell Method The Pronucleus Method
Transfer of genes to fertilized eggs or embryos.
The transfection of fertilized egg involves
either the transfer of whole nuclei or whole
chromosomes or their fragments or the DNA
segments.
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For the transfer of whole nuclei, The cells are
treated with cytochalasin B and enucleated. The
enucleated cells are incubated with the desired
karyoplasts for the induction in presence of
Polyethylene Glycol (PEG).
For transfer of whole chromosomes, metaphase
cells are subjected to hypotonic lysis and
individual chromosomes or fragments are isolated
and then icubated with whole cells / eggs for
transfection.
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Microinjection of DNA segments In this the
fertilized eggs are injected with DNA segments
for integration. DNA integrated eggs are then
used for getting transgenic animals.
Transfer of genes to cultured cells stem cells
are undifferentiated precursor cells, the genes
can be delivered through retroviruses or
Directly by techniques of microinjection using
particle gun, electoporation or by the use of
lysosomes.
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• Uses
• Transgenic animals are more efficient than their
  normal counterpart in feed assimilation.
• They exhibit faster growth and hence achieve the
  marketable size sooner.
• Meat quality is good.
• They are resistant to certain diseases.
• Serve as bioreactors for obtaining valuable
  recombinant proteins and pharmaceuticals from
  their milk or urine or blood.

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Transgenic pigs have also been produced by
fertilizing normal eggs with sperm cells that
have incorporated foreign DNA. This procedure,
called sperm-mediated gene transfer (SMGT) may
someday be able to produce transgenic pigs that
can serve as a source of transplanted organs for
humans
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Transgenic Chickens grow faster and in large
numbers can be grown in close quarters
synthesize several grams of protein in the
"white" of their eggs.
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