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INTRODUCTION Livestock Animals are a major source
of food, milk, wool, leather & many other byproducts.
Naturally has always been an interest in improving the
efficiency of livestock production. Until recently selective
breeding was the only way to enhance genetic features of
animals. however, this method is time consuming & can
introduce limited variation. New gene transfer techniques &
introduction of cloned genes into fertilized eggs, successful
implantation of modified eggs into receptive female & getting
progeny carrying cloned gene has resulted into development of
new area of transgenic animals.
Transgenic animal is a
fertile animal that carries an introduced gene(s) in its germ
line
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TRANSGENIC MICE
The aim of transgenesis is to produce animals with beneficial
traits. There are many difficulties faced in achieving success in
fish and farm animals, however, with mouse the transgenesis
experiments are not the one to yield any production but are meant
for experimental purpose. Transgenic mice serves as a model for
transgenic experiments. ability to produce a transgenic mice has
opened new approach to studying fundamental problems of
development & disease in mammals. Mouse is
appropriate choice because they have short generation time, super
ovulated mouse can yield up to 40 eggs, reimplantation is
relatively easy & mouse can carry up to 20 offspring.
PRODUCTION OF TRANSGENIC
MOUSE Mouse is a model system
used for introduction of genes & expression of genes stably.
external genes or targeted mutagen of mouse gene are introduced in
germ line of fertile animals. This results in production of either
Chimera of mosaics. Mice with all tissues made up of introduced
DNA or transgene are chimera. Mosaics are animals carrying
introduced DNA in some & not all tissues. They may have DNA from
some other source also. Frequency of transgene depends on extent
to which the manipulated cells have contributed to germ cells.
chimeras or mosaics if have transgene in germ cells will pass it
to offspring by mendelian law. Established
routes of transgenesis of mice are:
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Microinjection of DNA into pronucleus
of fertilized egg,
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Retroviral infection of fertilized egg
at 4-8 cell stage,
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Genetic alterations of embryonic stem
cells & their introduction into blastocyst,
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Retroviral infection of embryo after
implantation into uterus
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