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Dolly, the first animal to
be cloned, was created using
the technique of somatic
cell nuclear transfer (SCNT).
To do this, cells are
taken from the animal that
is going to be cloned. In
the case of Dolly the sheep,
a cell was taken from normal
body cells – somatic cells -
in her udder. The nucleus of
these cells was removed.
Becasue the nucleus
contains all of the genetic
material to make the animal,
it is termed the donor cell.
Egg cells are used for
cloning because of their
ability to grow rapidly. The
egg cell’s nucleus is
removed and the nucleus from
the donor cell is inserted
in its place.
Dolly, the world
famous sheep - the first
animal to be cloned.
The egg is then exposed
to numerous stimulants which
activate the reconstructed
embryo, making it divide and
grow. The division of the
egg cell follows the same
process that would occur if
the egg was fertilised by
sperm during natural
reproduction.
The cell division
continues for 5 days until a
blastomere forms. A
blastomere is a ball of
nearly 100 cells all with
the same genetic material as
the donor.
Once a cloned embryo
reaches the blastomere stage
of development, it can
follow two paths. It can be
used as a source of stem
cells, or it can be
implanted into a uterus of a
female to create a whole
organism. This is called
reproductive cloning. When
Dolly was born, she was the
only lamb born from 277
attempts. She was a clone of
the sheep whose udder cell
was used.
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