A2 OCR syllabus specific on cloning animals and transgenic animals

1. Cloning Animals
Creating genetically identical
offspring

2. Embryo splitting- artificial identical twins
In this simple form a ram with desirable genes
is selected (e.g. long coat)
The ewe with desirable characteristics is also
chosen the egg and sperm are fertilized in vitro
The zygote is allowed to grow in vitro to 16
cells then split. The cell bundle can be split in
two or more and implanted into one or several
surrogate mothers.

3. Artificial cloning of animals
(nuclear transfer)
The most popular
method involves
removing the nucleus
from the body cell of
your animal to be
cloned (usually a
mammary cell)
Take an egg (ovum)
of the same species
and remove its
nucleus (enucleation)

4. Artificial cloning of mammals
Insert the genetic
information (nucleus)
from the body cell into
the ovum (electro
fusion)
Implant the ovum into
the oviduct of a
surrogate female
female to culture
Implant the early
embryo into a final
surrogate mother
Await birth!

5. Nuclear transfer method -
summary
In this the mammary cells are
removed from the desired
clone sheep
An egg cell (ovum) from
another sheep is enucleated
The mammary nucleus is
implanted into the enucleated
egg by electro fusion
This egg is ‘cultured’ in the
oviduct of another sheep and
finally implanted into the
uterus of a fourth
It took 277 attempts!

7. Nuclear transfer - using an
ovum/oocyte.
The oocyte had to be enucleated
to remove the unwanted genetic
material so only the ‘clone’ DNA
would be replicated.
The oocyte is large with extra
nutrients to enable development.
It is specialized for reproduction
and will begin to divide
spontaneously and implant in the
uterus.
These totipotent cells have the
capability of turning on any gene
in the genome.
.

8. Embryo splitting
This is a simpler method.
Sperm and egg are
selected.
They are fertilized in vitro
The zygote divides to a 16
cell embryo,
This is split into four or
more,
These are implanted into 4
surrogate mothers.

9. Advantages of cloning animals
There are hundreds of
cloned animals round
the world.
Desirable trait beasts
(e.g. leanest for meat
good milkers) can be
copied exactly with no
variation
Endangered species can
be copied.
Animals altered for
pharmaceutical
purposes can be copied.

10. Use of cloning to treat disease-
Neutrophils in the lungs
During a lung
infection it is
necessary for white
blood cells to get into
the lungs
This is achieved by
the white blood cells
producing elastase to
digest little holes in
the alveoli

11. Alpha Anti-trypsin
AAT is manufactured
by the walls of the
alveoli to prevent the
further breakdown of
the elastin by the
White Blood Cells.
In humans incapable
of producing AAT a
series of lung
infections can
seriously weaken the
lungs

12. Loss of elasticity
While inspiration is
unaffected, expiration
and so removal of
carbon dioxide
becomes less efficient
This can lead to
hyperventilation and
feelings of suffocation
It is similar in nature
to emphysema

13. How to treat the problem
Administering Alpha
Anti-trypsin is an
effective treatment to
prevent this elastin
breakdown
Currently the main
source of AAT is from
blood donations

14. milk
Tracey the sheep.
An egg from a ewe was
fertilized with a sperm
from a ram in vitro.
A plasmid containing the
human gene for AAT
production was then
inserted into the egg using
a micropipette
The zygote was
transferred back to the
mother’s womb
After many attempts the
world’s first transgenic
ewe (Tracey) was born
Tracey (transgenic ewe)

15. The success of transgenic ewes
Tracey produces 35g
of AAT in every litre of
milk which is an
enormous amount.
The genes for making
AAT were passed to
some of her ewe
lambs
A mere 2000 ewes like
Tracey would produce
enough milk to supply
all the hospitals in the
world.

16. Disadvantages of cloning
Dolly the sheep died of
lung cancer (the initial
report of premature ageing
was wrong) It is still
unclear whether cloning
animals with older genetic
material is detrimental to
the health of the clone
It is costly – low success
rate expensive technology
A clone flock (genetic
uniformity)would soon be
wiped out by a disease to
which their genetic type
was susceptible

17. Non-reproductive cloning
Also known as
therapeutic cloning.
Biotechnology has
already enabled
Biologists to artificially
produce simple organs
such as bladders to
replace those removed
due to bladder cancer.
Using the individual’s own
cells to produce new
organs eliminates the
problem of rejection.