Cloning
Cloning in Animals
Organisms that are genetically identical
are clones
 Asexual Reproduction always
produces clones
 Laboratory Techniques have been
developed that have allowed this to
happen in Animals
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Wishful Thinking!!!
Cloning in Plants
Plant Cloning
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1950’s first experiments done with Frogs.
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When Transplanted nuclei from cells of Tadpoles
and Frog Embryos into egg cells that had their
nuclei removed(Briggs and King) They found that
many of the eggs would develop into tadpoles if the
source of the original nucleus was the early
embryo. When they took Tadpole nuclei they
would not.
Also found that the tadpoles that did arise would
not develop into adults
Results gave support to the idea that differentiated
cells could not be used to create clones
Impossible becomes Possible
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Early 1990’s some success found with
Mice
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Mice were cloned by using nuclei of cells
taken from Mice Embryos
Heres Dolly!!!
Wilmut et al. Produced “Dolly” in 1997
 Used Genetic Information Taken from
Udder of Adult Sheep
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In order for differentiated cells to be cultured
to produce an undifferentiated embryo the
process of Cell Differentiation had to be
reversed.
Cloning - Steps
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Unfertilized Eggs Collected from a donor sheep and had nuclei
removed
From 2nd Animal removed a sample of Udder cells. These Cells
were cultured and had cell cycle arrested during the G Phase
Nuclei from Udder Cells Transplanted into the egg cells.
Resulting Cells were cultured and a few began to divide.
These early embryos implanted into a surrogate mother. One of
these developed into a Lamb – Dolly
DNA Tests confirmed that the Lamb was identical Genetically to
the Sheep that had provided the Udder Cells
Problems
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Other Researchers have repeated the
work but as more examples are created
there is evidence that there are health
problems associated with the Cloned
Animals. Dolly showed signs of
Premature Aging.
Human Cloning
Very Controversial Topic
 Difference Between:
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Therapeutic Cloning – Culturing of Human
Cells for use in Treating Medical Disorders
 Reproductive Cloning – Development of a
cloned human embryo for the purpose of
creating a cloned Human Being
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How is Therapeutic Cloning Done?
Eggs are coaxed to mature in a culture dish. Each has a remnant egg cell
called the polar body and cumulus cells from the ovary clinging to it.
While an egg is held still with a pipette, a needle is used to drill
through the zona pellucida, removing a plug.
After ejecting the zona plug, the needle is inserted back in the egg
through the hole to withdraw and discard the polar body and the
egg's genetic material.
A cumulus cell from another egg is taken up into the needle. Cells
called fibroblasts (or their nuclei) can also be used in this step.
The cumulus cell is injected deep into the egg that has been stripped
of its genetic material.
The injected egg is exposed to a mixture of chemicals and growth
factors designed to activate it to divide.
After roughly 24 hours, the activated egg begins dividing. The cells
contain genetic material only from the injected cumulus cell.
By the fourth or fifth day, a hollow ball of roughly 100 cells has
formed. It holds a clump of cells called the inner cell mass that
contains stem cells.
The blastocyst is broken open, and the inner cell mass is grown in a
culture dish to yield stem cells.
The stem cells, in turn, can be coaxed to grow into a variety of cells
that might one day be injected into patients.
Controversy
Proponents of Therapeutic Cloning
argue that this may provide key to
eliminating Disease
 Yet all means of cloning does result in
the creation and destruction of hundreds
of embryos.
 Cloning Technologies have the potential
to change the definition of life.
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