FIND OUT MORE. Cells 73 • Farming 66 • Genetics 209 • Growth 149 • Nervous System 138 • Reproduction 148
Science and Technology^211
The starter cells in an embryo are
called stem cells. As the embryo grows,
stem cells change to become the
different cells needed in the body,
such as nerve cells and blood cells.HOW ARE ANIMAL CLONES PRODUCED?
The first clone made with DNA from an adult animal
was Dolly the sheep in 1997. DNA was taken from an
adult sheep (Dolly’s biological mother) and inserted
into an egg cell (with its own DNA removed) from
another sheep. The cell started to divide, and the
embryo was taken and put into the womb of a third
sheep – Dolly’s surrogate (birth) mother. Animal
clones could be used for medical research.Clones are different individuals with the same genes. Clones are
common in nature – a bacterium clones itself by splitting in two,
producing two identical bacteria. Now scientists have developed
artificial cloning techniques that work with mammals.WHY IS THERE CONCERN ABOUT IT?
Stem cell research is controversial because the cells
are taken from human embryos that have been
fertilized in the laboratory. To avoid rejection of the
cells the embryo should ideally have been cloned
using the patient’s DNA. Many people have concerns
about using human embryos in this way.HOW CAN STEM CELL RESEARCH HELP PEOPLE?
Stem cell research is investigating the use of stem
cells to repair damaged or diseased tissue. For
example, the body cannot repair or replace nerve
cells damaged by disease or injury. Transplanted
stem cells could be grown to develop into new nerve
cells to treat Parkinson’s and Alzheimer’s diseases.COULD HUMAN BEINGS BE CLONED?
In principle, humans could be cloned in the same way
as Dolly, perhaps to help a person unable to have a
child in any other way. But, as with other aspects of
genetic engineering, human cloning is controversial,
and has already been banned in many countries.4 INTRACYTOPLASMIC SPERM INJECTION (ICSI)
ICSI is used to help couples who have difficulty conceiving a baby.
The father’s sperm is injected into an egg from the mother. In cloning,
the procedure is different. Instead of injecting sperm, the nucleus of
the egg cell is removed and replaced with the nucleus of a mature
cell from the mother. Sperm is not needed.HOW ARE BANANAS CLONED?
Many plants propagate (reproduce) vegetatively
(without sex). Each new plant has the same DNA as
the parent and is therefore a clone. On a plantation
all the banana plants are clones of their parents.1 STEM
CELL RESEARCH
This electron microscope image
shows stem cells from an adult’s
bone marrow. These are the only
type of stem cells that occur in
an adult’s body. These stem cells
change to produce different
blood cells, but only embryo cells
can produce all the different cells
that make up a human being.CLONES
DOLLY THE SHEEP 1
Dolly’s biological mother was
six years old when her DNA was
cloned to produce Dolly. Sheep
can live for 11 to 12 years, but
Dolly died when she was six.STEM CELLS
Leaves
designed to
grow using
less fertilizer