CLONING - tissue culture methods and uses explained
Descriptions of cloning techniques applied to plants and animals
Doc Brown's Biology Revision Notes
Suitable for GCSE/IGCSE/O level Biology/Science courses or equivalent
This page will help you answer questions
such as ...
What are clones?
How do you make clones?
What are clones used for?
See also section on
There are two ways of producing cloned plants.
1. Tissue culture technique
You first select cells from a plant which has
Here you put a few plant cells into a dish of
an artificial growth medium that also contains hormones.
The cells grow quickly into new whole plants, all of
which are clones of the original parent plant.
These cloned plants can be grown very quickly
using little space in a controlled nutrient medium and can be
cultured at any time of the year - seasons don't count anymore!
Remember these are clones - genetically
This tissue culture technique is used by or
(i) biology scientists (botanists in this
case) to preserve rare plants that are difficult to reproduce
naturally - especially important now that many habitats are
under threat from human activity in the landscape and
unfavourable climate changes.
(ii) Horticulturalists can produce lots of
stock of plants in their nurseries very efficiently and quickly.
(iii) You can use tissue culture to create
genetically identical lines of plants with beneficial traits
e.g. fruit taste, fruit yield, pesticide resistance - but these
are NOT genetic modifications.
2. Using cuttings from plants
This is a traditional older method, and
simpler to apply than tissue culture described above.
Many experienced gardeners take cuttings
(small sections of tissue) from
good healthy parent plants and then plant the cuttings in compost
containing hormones to
produce genetically identical copies of the parent plants.
The best tissue for this technique is
obtained from fast-growing root or shoot tips or a cutting with
a bud on it.
The samples should be kept in moist
conditions until ready for use.
Again, these plants can be produced quickly
and cheaply both by professional or amateur gardeners.
animal clones using embryo transplants
Farming uses many new methods thanks to advances
in 'biotechnology' e.g.
Farmers can produce cloned offspring from their
prize bulls and cows using embryonic transplants.
Sperm cells are removed from a prize bull and egg
cells taken from a prize cow.
The sperm are used to artificially inseminate
(artificially fertilise) the egg cells.
The embryo that develops can be split many times
to form clones - but before any cells become specialised.
The cloned embryos can be then implanted into
The embryos can then grow and develop in the
normal natural way to produce lots of genetically identical baby calves.
'Theoretically', hundreds of ideal offspring can
be derived every year from just one best bull and cow parents.
adult animal cells
You can take an unfertilised egg cell and remove its
nucleus in the technique of adult cell cloning.
The nucleus is extracted from an adult body cell (e.g.
skin cell) and inserted into the 'empty' egg cell.
So you have replaced one nucleus with another,
therefore changed the genome.
The egg cell is stimulated with an electric shock,
causing it to divide, which is exactly what happens normal embryonic
When the embryo has developed into ball of cells, it
is implanted into the womb of an adult female.
The embryo then grows into an identical copy of the
original adult body cell and therefore a clone with the identical genetic
information - same genome.
The most famous clone is Dolly the sheep, the
forerunner of a scientific revolution!
cells using selected tissue
A sample of the tissue is selected and extracted from
an animal, made up of the cells you wish to study.
The cells you want are separated from others using
The separated cells are added to a culture vessel
of a growth medium containing all the nutrients that they need to grow
After a number of cell divisions the sample can be
split and the growth repeated in other vessels.
The cell culture product can then be stored until
required for experiments.
Animal tissue culture can be used in medical research
to produce large quantities of cells in isolation from the rest of an
animals body - no complications from the rest of the organism when
conducting tests with them.
You can use these cells to conduct experiments
e.g. the effect of drugs or any other chemical substances on the
e.g. the effect of glucose on pancreatic cells
grown in the culture medium.
You can look at the health of cells in different
mediums - effectively different environments.
concern about cloning - 'pros and cons'
(a) Although cloning enables you to produce plenty
of supposedly 'ideal' offspring, there is a genetic price to pay.
Using cloning techniques, you do reduce the
This means there are fewer alleles in the
population and consequently the animal is more susceptible to
When members of a population are so closely
genetically related, and encounter a new disease, the
whole population can be affected, possibly fatally.
The animal's genome may not have the alleles
necessary to offer some resistance - protection against the disease.
Cloned animals might not be as healthy as
normally produced offspring.
e.g. Dolly the sheep had arthritis which
you expect in old age in many animals.
There are other cases where animal's
organs do not seem to function as well as expected.
These effects are not that well understood
at the moment.
(b) One important use of cloning is to help
preserve endangered species of animals.
Cloning could be used to
reproduce endangered animal species, whose numbers were falling dangerously
low i.e. in danger of extinction.
(c) Research on cloning animals has led to a
greater understanding of embryo development and also the process of
ageing and age-related disorders.
(d) There is concern that attempting to clone
humans might not be very successful.
Because of the reduced gene pool, the
offspring may be more likely to suffer from genetic disorders
including babies born with severe disabilities.
(e) Cloning mammals is proving a means
providing organs for transplants.
e.g. genetically modified pigs can be
bred to provide donor organs for humans and cloning the pigs could meet the
ever increasing demand from critically ill patients on the waiting list.
Typical learning objectives for this page
Know and understand that asexual reproduction can be used to
produce individuals that are genetically identical to their parent.
Appreciate that scientists
can now add, remove or change genes
to produce the plants and animals they want.
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