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Disease Control
One of the most important developments
has been a vaccine for hoof and mouth disease, which
causes cores in the mouths and hooves of animals,
making them weak. It is caused by about 60 related
virus types. The first vaccine for hoof and mouth
disease developed using recombinant techniques is
made of a protein called VP3, one of four proteins
that make up the surface of the virus. The protein
is spliced into the genes of E. coli bacteria. This
vaccine works on one of the 60 virus types. Vaccines
for hoof and mouth disease have been developed to
combat all the viruses, but the vaccine’s effect
is temporary.
Growth Promotion
Mill and meat production can be increased
by hormones made by gene-spliced bacteria. Drugs
that promote growth remain in meat after it’s butchered,
but genetically engineered meat and milk result
in increased production without harmful residues.
Cloning
Cloning is the asexual reproduction
of an organism in which the offspring is the result
of a single parental cell. Cloning does happen in
nature naturally. Plants that grow from cuttings,
single-celled organisms that reproduce by dividing,
and jellyfish that reproduce by bidding are all
examples of cloning in nature. Parthenogenesis is
the phenomenon in which an offspring is developed
from the nucleus of an unfertilized egg. “Parthenos”
means “” and “genesis” means “origin”. Male
bees are formed this way as they are the offspring
of the queen bee alone. Plants have been propagated
by cloning single cells in tissue cultures. These
include strawberries, asparagus, pineapple, African
violets, and carnations. The Venus Flytrap was saved
from extinction after being driven out of its native
habitat by being propagated by cloning. To clone
plants, scientists place tiny slivers of a plant
in nutrient solution for several months. The cells
multiply and when transplanted, put down roots.
This method is used in forestry and agriculture.
The first successful mouse cloning
experiments were conducted in 1981 in Switzerland
and the United States. Cell nuclei were taken from
the inner cell-mass of an early stage gray mouse
embryo. The nucleus was inserted into the fertilized
egg of a black mouse. The original material was
removed from the egg, leaving the new material.
The eggs were then transferred to the wombs of white
mice who had been treated with hormones for pregnancy.
In these early cloning experiments, 542 transplants
had to be performed in order to produce three cloned
mice offspring. They were completely like the donor
of the gray mouse cell nuclei, and not at all like
the donor of the egg or the surrogate mother who
carried them. in 1997 Scottish geneticists cloned
an adult animal. They removed the nucleus of the
cell from a sheep’s egg cell. They then took the
egg cell (which had had the nucleus removed) and
put another nucleus in it taken from the udder of
another sheep. The genetically engineered cell was
placed in a host mother sheep. The resulting sheep
was a clone of the sheep from whose udder the cell
nucleus was taken.
Diagrams of bovine cloning process:
www.infigen.com/process.htm
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