TOPIC 3: REPRODUCTIVE CLONING
TECHNOLOGIES
• Cloning in horticultural practice
• Artificial cloning of mammals
CLONING
• Embryo Splitting
• Nuclear Transfer
• Application of Cloning
CLONING: WHAT IS IT?
Definition: the process of making an
identical copy of an original.
There are different types of cloning
procedures:
• Cloning in horticultural practice
• Artificial cloning of mammals:
• Embryo splitting to make identical
copies
• Somatic cell nuclear transfer (SCNT)
CLONING in horticultural practice
Plant tissue culture technology in the lab identical copies of a
plant
Examples: ornamental plants (orchids), native plants (eucalyptus)
ADVANTAGES:
• Slow growing plants produced in large numbers
• Plants cultured year round in controlled conditions
• Virus free tissue can be used
• Cultured plants transported from country to country
CLONING in horticultural practice
STEPS:
1. Plant with desirable characteristics selected
2. Pieces are selected with meristematic tissue
Can be done using:
• whole
organisms,
• Tissue samples
or
• even a single
cell
CLONING in mammals
EMBRYO SPLITTING
Cells of an early embryo artificially separated into two cell masses
Mimics natural process of identical twins
Embryo features:
• Parents chosen due to desirable characteristics
• Embryos produced through in vitro fertilisation
• Fine glass needle splits embryo at early stage of development
• Each embryo is implanted into uterus of surrogate female parent
BIOLOGICAL CLONING: EMBRYO
SPLITTING
1.
Egg cells are removed from the
donor female and fertilised in
vitr o by a sperm from the male.
2.
After the fertilised egg has
divided, the coat around the cells
that promotes cell division is
removed and the two cells are
separated.
3.
Each cell is then given an
artificial coating that promotes
cell division, allowing for the
differentiation of embryos.
4.
These embryos are then
implanted into surrogate
mothers.
CLONING in mammals
Embryos
• not identical to either
parent
• Only identical to each
other
• Identical copies of the
fertilized egg
CLONING in mammals
SOMATIC CELL NUCLEAR TRANSFER (SCNT)
Cells and their nuclei are manipulated using SCNT
a) The nucleus of a cell is removed creating an enucleated cell
b) The nucleus of another cell can be transferred to an
enucleated cell to form a redesigned nucleated cell
c) An enucleated cell can be fused with a somatic cell using a
short electrical pulse.
CLONING in mammals
BIOLOGICAL CLONING: NUCLEAR
TRANSFER
1. Nucleus collected
from adult
somatic cell
2. Unfertilised egg
cell is enucleated
3. Fusion of
nucleus and
donor egg
4. Implantation of
embryo to surrogate
mother
5. Development & birth of
organism with identical
genotype to adult from
step 1.
CLONING in mammals
SOMATIC CELL NUCLEAR TRANSFER (SCNT)
Genetic information comes from nucleus of adult body cell so
genotype of cloned animal determined by donor nucleus, not the
egg into which the nucleus is transferred.
THE DOWNSIDE:
• Success rate in initiating development of the egg cell after
transfer of the donor nucleus is low
• High levels of developmental abnormalities
CLONING: APPLICATIONS TO
AGRICULTURE
• Animal cloning is used to increase the
number of breeding animals with naturally
occurring desirable traits.
• Plants are “cloned” from cuttings in order
to have the exact same desirable
characteristics that may not appear in seed
offspring. However, this can also leave
plants with a lower genetic diversity and
more vulnerable to pests and disease
infestation.
• Cloning can also be used to conserve rare
or endangered plant species, such as the
Wollemi Pine, which was thought to be
extinct and dates back to an existence of
110 million years ago.
CLONING in mammals
SAMPLE PROBLEM:
• Scientists took tissue from three cattle that they believed had
been created through a cloning process. The cattle all had
identical genomes; however, their genome was not identical to
the mother who provided her genetic material via her eggs.
What type of cloning has been used to create the three cattle? (3
marks)