The document discusses genetic engineering techniques such as cross-breeding, cloning, and inserting genes from one organism into another. It provides examples of how genes for beneficial traits have been transferred between plants and animals to produce offspring with desired characteristics. The document also describes how genetic engineering allows single genes to be transferred between unrelated species using techniques like inserting genes into bacteria or modifying plant and animal stem cells.

1. Manipulating genes
© Sir Ralph Riley

2. Ever since humans have been domesticating animals and raising crops
they have been (unwittingly) manipulating genes
By cross pollination and cross breeding they have tried to introduce
the beneficial characteristics of one variety into a different variety
of the same species*
For example, a bull born to a cow that has a good milk yield, might
be mated with a cow from a low-yielding stock, in the hope that the
offspring will inherit the characteristics which lead to a high milk yield
This has been done for thousands of years without any knowledge
of genes or the mechanism of inheritance
Cross breeding
2

3. In the following (hypothetical) example, a variety of high yielding
wheat which has poor resistance to disease…
…is crossed with a variety which has good disease resistance but
gives a poor yield
The gene* for ‘high yield’ is represented by H
The gene for ‘low yield’ is represented by h
The gene for ‘good disease resistance’ is represented by R
The gene for ‘poor disease resistance’ is represented by r
Crossing
3

4. HHrr
high yield
low resistance
pollen
grain
ovule
hhRR
low yield
high resistance
The F1 consists of
plants with high yield
and good resistance
zygote
4

5. Can you see any disadvantages in this method of
manipulating genes ?
Try working out what would happen if you tried to breed from
the F1
Work out the various gene combinations in the gametes
Put them into a
4x4 Punnett Square
5

6. F1 cross HhRr x HhRr
Possible combination
of genes in gametes HR Hr hR hr
HR Hr hR hr
HR
Hr
hR
hr
HHRR HHRr HhRR HhRr
HHRr HHrr HhRr Hhrr
HhRR HhRr hhRR hhRr
HhRr Hhrr hhRr hhrr
The F1 does not breed true. Of the 16 possible combinations
of genes, 7 do not have the combined beneficial genes
F1 cross 6

7. a b c d e
a x b = c c x d = e
Hybrid wheat (c) was
crossed with wild
wild grass (d) to give
hybrid wheat (e) used
for making flour and
bread
Manipulating genes
by cross breeding
Wheat variety (a)
was crossed with
wild grass (b) to
give
hybrid wheat (c)
wheat
© Sir Ralph Riley
7

8. Interbreeding transfers the complete genome of one variety to
another.
This means that many new and unpredictable gene combinations
may be formed in addition to those intended
This method of genetic recombination can take place only between
varieties of the same or closely related species
Genetic engineering makes it possible to transfer single genes
The genes can also be transferred from one species to a totally
different species
Genetic engineering
8

9. There are several ways in which genes from one organism can be
inserted into a different organism
They can be coated on to microscopic gold particles and ‘fired’
into the cells
They can be delivered by viruses
They can be transmitted by using structures, called plasmids,
present in bacteria
For example, the human gene for making insulin can be transferred
to bacteria, which are then allowed to reproduce in a culture medium
from which the insulin can be extracted
Plasmids
9

10. in addition to a loop of DNA… …bacteria also contain numerous
rings of DNA called plasmids
cell wall
cytoplasm
cell membrane the plasmids can be
extracted and used for
genetic engineering
0.001mm
A bacterium 10

11. plasmid
restriction
enzyme cuts
plasmid
the same
restriction
enzyme cuts
the insulin gene
out of the
human DNA
human DNA
strand
insulin
gene
Inserting a gene
the insulin gene
is inserted into
the plasmid
11

12. The recombinant plastids are
inserted into a bacterium *
the insulin gene makes the
bacterium produce insulin
Recombinant plastids
12

13. Only about 1 in 100,000 bacteria take up the recombined plasmids
There are techniques for identifying and isolating these bacteria
The bacteria with the insulin gene are then allowed to reproduce
in a culture solution from which the insulin can be extracted*
Human growth hormone can be made in a similar way
Factor VIII, needed by haemophiliacs, (blood clotting disorders)
can be produced from hamster cells containing plasmids with the
factor VIII genes
Chymosin, used for clotting milk in cheese-making, can be
produced from yeast cells with recombinant plasmid DNA
Applications
13

14. As well as producing useful substances from genetically
altered cells, whole organisms can be genetically modified.
Some examples are ….
A bacterial gene which makes an insecticide can be introduced into
crop plants, e.g. maize and cotton, to make them resistant to attack
by moth caterpillars
A gene which confers resistance to herbicides has been inserted
into crop plants so that spraying kills weeds but not the crop plants
A gene introduced to oilseed rape makes the oil more suitable
for commercial processes, e.g. detergent production
Genes which control the production of human enzymes have been
inserted into sheep so that the enzymes can be recovered from
their milk
Applications
14

15. Genetic engineering does not always have to involve gene transfer
between unrelated organisms
Genes in a single organism can be modified to improve their
characteristics or their products
A gene for the production of ß carotene (a precursor of Vitamin A)
has been introduced to rice to benefit countries where rice is the
staple diet and Vitamin A deficiencies are common*
The next slide shows tomatoes which have been genetically
modified to suppress production of an enzyme which causes the
fruit to soften as it ripens. This improves the keeping qualities
Applications
15

16. Genetically modifiedGenetically modified tomatoesControl tomatoes
After storage After storage
© AstraZenecaTomatoes

17. Opponents of genetic engineering stripped the bark off these poplars
in order to kill them.
A gene had been inserted which softened the cell walls so that fewer
environmentally damaging chemicals were needed in paper-making.
17

18. When organisms reproduce asexually, all the offspring receive a full
set of genes from the parent.
As a result they are identical to each other and to the parent
Examples are
Bacteria and single-celled organisms
Plants with vegetative reproduction by bulbs, corms etc.
Fungi
Some of the lower invertebrates
A population of identical individuals arising from asexual
reproduction is called a clone
Cloning
18

19. A clone of crocuses
19

20. Next slide

21. Vertebrates do not reproduce asexually but clones can be produced
artificially
In some cases this is done by transferring the nucleus from a body
cell to an egg cell (ovum) from which the nucleus has been removed
The following slide illustrates one of the first successful
techniques for cloning a mammal
20

22. cells in sheep A’s
mammary gland
one cell
isolated
diploid
nucleus
egg cell (ovum)
from sheep B
nucleus
removedthe two cells
are fused together *
embryo implanted
in uterus of sheep C
cloned lamb
born
cell division produces
early embryo
Dolly
21

23. If the process becomes cheap and reliable it means that beneficial
genes will be present in all the offspring, thus eliminating the
chances of their being lost during conventional breeding
Before the early embryo is implanted in the surrogate mother, it can
be broken up into its individual cells. Each of these can develop into
a new embryo
Sheep, pigs, horses, cows and, by now, probably many more animals
have been cloned
So far, this is being done on an experimental basis
Hundreds of embryos have to be prepared and implanted to obtain
one or two successful births
22

24. fertilised frog egg
cell division to form
an embryo
growth and development to
produce tadpole and frog
at the 8-cell stage, any one of these
cells can develop into a frog
23

25. 8-cell frog embryo
cells separated
each cell can develop into a frog
Clone of frogs 24

26. The cells from the 8-cell embryo are called embryonic stem cells….
…because each one can form all the cells and tissues to
produce a complete frog
After the 16-cell stage, the cells lose this ability and can only
produce specialised cells such as blood, bone and nerve cells
Cells capable of dividing to produce specialised cells are
called stem cells
Specialised cells normally lose the power to divide and may have
a limited life span
25
The tissues produced by specialised cells usually contain some
stem cells which retain the power of division

27. section through skin
epidermis
dermis
basal layer
hair
fat layer
basal cells
(skin stem cells)
these stem cells keep
dividing and pushing
new skin cells to the
outside
cells dividing
cells worn away
2mm
Skin stem cells
26

28. stem cell in red
bone marrow
produces ……..
red cells
several types
of white cell
platelets
Blood stem cells
27

29. Skin stem cells can normally give rise only to skin epidermal cells
Bone marrow stem cells can normally give rise only to 6 types of
blood cell
But embryonic stem cells can produce all the cells of the body
Human embryonic stem cells can be obtained from 10 day embryos*
These embryonic stem cells can be cultured in a special nutrient
solution
28

30. section through a 10-day
human embryo
0.5 mm
these cells will contribute
to the placenta
these cells will form
the embryo (stem cells)
stem cells cultured
(cloned)
nutrient medium*
stem cells transferred
to culture dish
Human ESCs
29

31. All the cells in the body have a full set of genes
When the cells become specialised, they lose their ability to divide
and many of the genes are ‘switched off’
For example, the genes for producing hydrochloric acid in a stomach
cell would not be functional in a skin cell
Even though tissues consist mainly of specialised cells, most of them
also contain their own stem cells
It may become possible to treat stem cells from specialised tissues
with hormones and growth factors that cause them to produce a
wider range of specialised cells*
30

32. Applications of stem cells
Most applications of stem cells are in the experimental stage, are
undergoing clinical trials or have been tried on very few patients
Possibilities are
Replacement of damaged tissues such as heart muscle, skin,
bone and cartilage
Treatment of disease, e.g. diabetes by injecting islet cells
into the pancreas; or Parkinson’s disease by injecting nerve
stem cells into the brain
If the stem cells can be derived from the patient’s own tissue,
rejection by the immune system is avoided
31

33. Question 1
What are the possible gene combinations in the gametes
From genotypes AAbb and aaBB ?
(a) Ab
(b) AB
(c) ab
(d) aB

34. Question 2
Which of the following statements is correct?
F1 hybrids from cross breeding or cross pollination…
(a) …may not be able to reproduce
(b) …can contain genes from unrelated species
(c) …may contain unwanted gene combinations
(d) …may not breed true

35. Question 3
Genetic engineering can
(a) Transfer genes only within a species
(b) Transfer single genes between species
(c) Create new species
(d) Modify a species

36. Question 4
The bacterial components which can be used to transfer
genes are
(a) mitochondria
(b) DNA
(c) plasmids
(d) proteins

37. Question 5
DNA which has been genetically engineered is called…
(a) Engineered DNA
(b) Hybrid DNA
(c) Modified DNA
(d) Recombinant DNA

38. Question 6
Which of the following can be made by genetically
engineered bacteria ?
(a) Human insulin
(b) Human growth factor
(c) Blood-clotting Factor VIII
(d) Blood platelets

39. Question 7
Which of the following could be described as a clone ?
(a) A litter of kittens
(b) A clump of daffodils
(c) A bacterial culture
(d) An F1 hybrid

40. Question 8
A cell is removed from cow P. An ovum is obtained from cow Q
and its nucleus is removed. The cell from P is fused with the
enucleated ovum from Q. The combined cell starts to form an
embryo which is transplanted into the uterus of Cow R and in due
course a calf is born.
Which of these cows is the biological parent of the calf?
(a) P
(b) Q
(c) R
(d) The calf does not
have a biological parent

41. Question 9
Which of these statements is correct ?
(a) All cells can produce new tissue
(b) Only stem cells can produce new tissue
(c) Stem cells can divide
(d) All cells can divide

42. Question 10
Embryonic stem cells differ from other stem cells because …
(a) They can produce only one type of tissue
(b) They can produce a complete organism
(c) They can produce all kinds of cell
(d) They cannot be cloned

43. Answer
Correct

44. Answer
Incorrect