Genetic Engineering - techniques - splicing genes with enzymes! Uses e.g. making insulin, GM crops
and medical applications -
contemporary examples of biotechnology
school biology revision notes: GCSE biology, IGCSE biology, O level
biology, ~US grades 8, 9 and 10 school science courses or equivalent for ~14-16 year old
students of biology
What do we mean by genetic engineering?
Discuss the 'Pros and Cons' Be able to describe the basic principles of how to
transfer a gene from one organism's genome to the genome of another organism. Can you describe some uses of genetic
engineering in medicine or agriculture? Note: GM is used as an abbreviation
for genetically modified products i.e. the produce of genetic engineering
Sub-index for this page
Introduction to genetic engineering
The production of insulin
Examples of modifying the genomes of plants
More on agricultural and horticultural uses of GM products
Uses of genetic engineering in medicine
including gene therapy
Ethical & other issues: 'pros and cons'
of using genetic
modification in plants & animals
Thoughts on GM and the world production of food
The basic idea of genetic engineering
is to transfer a gene that gives rise to a desirable characteristic (trait)
from one organism's genome to a different organism's genome, so that it
acquires that desired characteristic.
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Production of insulin
- as an
example of the medical use of genetic engineering in biotechnology
BUT, still one more complication!
Unfortunately, not all the host cells
will have been modified correctly e.g. a faulty vector transfer.
Therefore in the final stage, you have to
be able to select and identify the individual host cells that
have successfully incorporated the desired gene.
Antibiotic resistance gene markers are
used to identify the correctly modified host cells.
A marker gene coding for antibiotic
resistance is inserted into the vector plasmid at the same
time as the gene for the desired characteristic.
The host bacteria are grown in a special
vessel containing antibiotics.
Only the bacteria containing the marker gene
will be able to survive and reproduce, because the antibiotics will
kill the rest of the cells that were not genetically modified
Working two genes in tandem! Clever stuff!
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of genetically modifying a plant genome
for enhanced characteristics
As we have seen, plants can be genetically modified to
enhance desired characteristics.
GM technology allows the transfer of useful
genes into plants, so they develop useful enhanced characteristics
e.g. anti-pest or increased size of grain.
GM crops are controversial but genetic engineering
is transforming crop production.
You can genes from all sorts of organisms, not
necessarily plants, cut out a selected chromosomes-genes, and insert
them into the cells of crop plants.
These crop plants are thus genetically
modified and referred to as GM crops.
You can genetically engineer crop plants to be
resistance to disease from e.g. viruses, increase crop yields,
produce bigger and better quality fruit.
A GM potato has been produced that is
resistant to potato blight, a disease caused by a fungus, that
devastated the rural population of Ireland in the 1840s who heavily
relied on the potato in their diet.
Note that when genes are transferred to
plants, it must be done at an early stage of their development
because older organisms have too many cells needing to be
The examples below
describe techniques used in agriculture to produce crops with desirable
characteristics that increase crop yields.
Example 1 Producing plant cell clones
Diagram showing the genetic modification of plant
cells using a bacterium plasmid vector, and finally cloning the plant cells
to produce a commercially viable plant on a large scale.
Scientists frequently use a bacterium call Agrobacterium fumefaciens to genetically modify plants.
The Agrobacterium fumefaciens bacterium
invades plant cells and can insert its genes into the plant's genome
With reference to the diagram above.
Stages 1. to 5.: A gene is taken from the
cells of a herbicide
resistant plant (B) and inserted into a
plasmid extracted from the Agrobacterium fumefaciens bacteria
The procedures use splicing genes to cut
the DNA strands open and join them up to make the modified
for even more details).
By this procedure, you can now introduce
the plasmid vector into the bacterium.
Stage 6.: The genetically modified plasmid is inserted back
into the bacterium.
Stage 7.: The bacterium, with the newly inserted gene, can
then enter the target plant cells and genetically modifies the plant
You quite simply let the modified bacterium
the plant cells, modifying their DNA.
Thus you can now clone the plant cells.
Stage 8.: BUT, you have to select the
correctly modified cells which have taken up the gene and reject the
rest of the cells.
After screening, the selected plant
cells are then grown into plantlets in a tissue culture
containing nutrients and growth hormones.
Stage 9.: The plantlets are then
trialled to produce fully grown mature plants.
Initially in a greenhouse, if successful,
full scale field trials using a much larger area.
The modified plant cells can then be used to grow
mature plants with their newly acquired gene giving them the
Example 2 Producing a crop plant with insect
A bacterium called Bacillus thuringiensis
produces a toxin (a protein) that is poisonous to insect larvae
that feed on plant roots and the adults on the leaves, damaging the
The gene in the bacterium that codes for the
toxin is inserted into the genome of crops such as corn and cotton.
The crops produce the toxin protein in their
stems and leaves giving the plants insect-resistance.
The toxic protein is specific to insect pests
(important) and harmless towards to animals, including humans and
other harmless insects - but the long-term effects of the
genetically modified genome are unknown.
This method, in principle, is good for farming
because it increases crop yield, less eaten by insects,
and reduces the use of insecticides - less harmful chemicals in
the environment e.g. using less
insecticides is less damaging to ecosystems in the countryside.
BUT, there is often a BUT!
As the insects feed on the crops they are
constantly exposed to the toxin, so that later generations of the
susceptible insects may develop resistance to the toxin and no
longer die from its effects - so farmers may have to use other
Also, although it kills the caterpillar or
larvae, that eat the crops, it only works on some orders of
insects e.g. moths and butterflies - the most serious pests
Farmers can use other insecticides - but
these are already being overused - one of the main reasons for the
decline of bee populations in many countries.
(When writing this, I found from the
internet, that toxin-resistant strains of insects are already
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More on examples of the use of genetic engineering in
agriculture and horticulture
Be able to discuss an understanding of the advantages and disadvantages of genetic
engineering to produce GM organisms and their applications - how are they used?
to what effect?, including:
In agriculture and horticulture
Increase the content of beta-carotene in golden rice, bananas
or other crops
to reduce vitamin A deficiency in humans.
- A lack of vitamin A in the body can be fatal,
but a GM crop may help this reduce this deficiency in some people's
- Beta-carotene is essential for our bodies to
make vitamin A.
- Without beta-carotene in our diet, we can't
make vitamin A.
- Vitamin A is a fat-soluble vitamin that is
naturally present in many foods.
- Vitamin A is important for normal vision, the
immune system, and reproduction.
- Vitamin A also helps the heart, lungs,
kidneys, and other organs work properly.
- Vitamin A deficiency is common in many Asian
and African countries and can cause blindness.
- This is due to too little
beta-carotene or vitamin A in their diet e.g. there is too little in
their traditional rice crops, so in these areas there is a problem
of Vitamin A deficiency..
- Golden rice is a GM rice whose genetic make-up
contains two genes from other organisms which enable this variety of rice to
produce sufficient quantities of beta-carotene.
- The gene controlling beta-carotene production
was obtained from carrot plants and inserted into the genome of rice
- With golden rice as part of their diet, the
risk of vitamin A deficiency is reduced and less people are likely to go
(b) The production of insect-resistant and herbicide-resistant crop
- Crops can be genetically engineered to grow
and survive in drought conditions - lack of water puts a big
constraint on the quality and quantity of crop yields.
- You can modify the genetic make-up of plants
by inserting genes that help plants be more resistant to certain 'pests' e.g. fungal attack or
- Weeds are a nuisance to a farmer, they use up
nutrients in the soil and compete with the crop of e.g. grain,
reducing the crop yield.
- But, you can also make GM crops resistant to a
herbicide being used to kill all weeds in the field of growing crops i.e.
only the crop that you want survive and the weeds dies!
- As the crop grows the field is sprayed with
herbicide, the crop is unaffected and the weeds killed.
- This sounds good, BUT there is
considerable concern, with available scientific data to prove
it, about the use and effect of herbicides and insecticides on the
local ecology e.g. damage to wild flowers, and particularly insects
like important pollinating bees.
- In my locality I see very few wild flowers
growing near fields cultivated using 'modern' agricultural methods.
- All of these effects will help to increase
the quality and yield of a crop - particularly important food
crops like maize, wheat and barley.
A Gene that helps fish survive
in cold water has been inserted into the genome of a tomato plant to
help the plant survive in a colder climate i.e. the plant is able to
cope with lower temperatures than the original plant.
- (d) -
- (e) -
Medical applications of GM products
(need to check other pages for overlap)
- (a) The production of human insulin by
genetically modified bacteria (discussed in detail above).
- GM produced insulin production has
been described in detail above.
- The process overall is one of inserting the
human insulin gene into bacteria and growing the bacteria to produce lots of
insulin quickly and economically efficiently (cheaply!).
- The resulting, and efficiently produced, insulin can be used to treat people with
diabetes, and is an example of genetically engineering bacteria, in this
case to produce human insulin.
other medical applications, scientists have
transferred human genes into cows and sheep to produce useful proteins.
- You can 'manufacture' human antibodies used in
the treatment of arthritis, multiple sclerosis and some types of cancer.
- These useful proteins can be extracted from the
'host' animal e.g. from cows milk.
- It might be possible in future to use animal
organs grown specially for transplant operations - ethical issues!
(c) Medical researchers are trying to develop
genetic modification treatments for inherited diseases caused by faulty
- The idea is to insert correctly working genes
(the normal correctly working allele)
into the cells of people suffering from the disorder caused by
alleles of faulty genes.
- This technique is called gene therapy - a
sort of allele replacement technique.
- Gene therapy is at a very experimental stage,
but much is hoped from this technique.
- It is sometimes possible to transfer the
'working' gene when the organism is at an early stage of development.
- e.g. applying gene therapy to an egg or embryo so
that the organism develops with the characteristic correctly coded for
by the gene - correct genotype, giving the correct phenotype.
- However, the following description describes one
particular type of gene therapy involving cell exchange.
example of a gene therapy procedure
- A deactivated virus is used as a vector, but it
is quite difficult to replace genes effectively.
- (1) A normal human allele is inserted into the
virus vector - the altered virus.
- (2) Cells carrying the defective gene are removed
from the patient.
- (3) The altered virus is inserted into the cells
removed from the patient.
- (4) The modified cells are then injected back
into the patient.
- (5) Then, hopefully, the modified cells can then
carry out their function correctly.
- Problems encountered in gene therapy patients
- An overactive immune response, which in some
early cases was lethal - the modified cells were treated as foreign
pathogens by the immune system.
- Leukaemia cases occurred, probably due to the
- Genome editing
- Genome editing is emerging as a potential
biotechnology involving replacing or removing sections of DNA of an
- It is possible to do this using 'molecular
scissors' and the technique is improving all the time.
- (As I'm writing this in 2020, two female
scientists have been awarded the Nobel Prize in Chemistry for their work
in developing gene editing techniques. Emmanuelle Charpentier and
Jennifer A. Doudna developed the Crispr tool, which can change the DNA
of animals, plants and microorganisms with high precision.)
- Note that any successful gene therapy cannot
prevent the patient from passing on an inherited medical condition to
- It is only the patient's cells that are modified.
- Any modification of the reproductive cells (male
and female gametes) involves at least two immediate problems.
- (i) Extremely technically difficult to do,
- (ii) and poses major ethical problems as to the
right to carry out such a procedure - 'designer babies'.
- This type of gamete gene therapy is not allowed
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and many other
issues of 'pros and cons' of the products of genetic engineering plants & animals
scientific development there are usually
advantages and disadvantages
and not all can be predicted!
- It is not unreasonable to take the moral view
that all the people of the world should have
- that is sufficient nutritious food needed for healthy living.
- How far can GM crops contribute to global food
- There is no doubt they can increase crop yields
even when the plants are grown on poor soil or harsh environments e.g.
extremely hot or cold environments.
- Is it right to insert genes from one organism to
another, especially as the species are not related.
- We have the capacity to confer on organisms,
characteristics which do not have naturally?
- Do we have the right to insert human genes into
other animals changing their long evolved genome?
- Many have a religious point of view that the
World was created by God and we have no right to interfere with it -
this is the way things should be and ordained by a higher deity!
- Some people believe that genetic engineering is
never justified on any grounds - but tell that to people and their
children who have benefited from gene therapy!
- Again we see positive examples of the
use of genetic engineering, but there are, as ever!, issues and problems to
solve concerning the application of genetic engineering - use of
genetically modified (GM) products.
- 1. This is
new technology, new
'biotechnology' to be precise, and people quite rightly are concerned about
e.g. GM crops, though curiously enough, I've never heard anybody express
worries about GM produced insulin - the latest versions of which are
produced by GM techniques!
- BUT GM products have enormous potential to
solve problems in e.g. increased yields in food production, treating
genetic disorder diseases.
- For people living in poorer less developed
countries, the quantity and quality of food CAN be improved.
- It is no incidence that people in developed
countries, who have a relatively good diet to start with, are much
more concerned about the use GM crops, than people in poorer
countries, with their greater need for an improved food supply.
- 2. There are concerns as to whether GM crops
e.g. cereals or rice have the same nutrient contents (mineral ions, vitamins
etc.) as non GM crops.
- Are there are any risks to human health by
eating GM food products?
- 3. Are there any short or long-term effects
on our health from
consuming GM modified meat, grain or vegetable products etc.?
- By changing an organism's genome, you can't
predict whether problems will emerge for future generations (crops
- Are there any health issues? Any long-term
effects on consuming GM produced foods.
- Will a GM based food cause an allergic
reaction when eaten?
- In fact, will there be an increase in the
incidence of food allergies and will new allergies arise?
- This begs the question whether GM or non-GM
varities of the same food will have different allergic reactions or
similar or different rate of allergic reaction in a population?
- Research so far, (as far as I know!), the
differences have been proved - but its a controversial question!
- OR, might GM food be an answer to certain
Will GM plants spread
their genes and affect the
local diversity of the farmland and environs.
- Will there be any effects on food chains and
- e.g. Will GM plants becoming more
successful than local plants?
- Will this reduce biodiversity around fields
and the countryside in general?
- Will the abundance and variety of wild flowers and insects be affected
by using insecticides or herbicides with GM crops?
- See also point 5.
Will GM crops hybridise with other crops
or grasses to produce new strains of plant, again, these could affect the
original biodiversity of the local flora (plants) and fauna (animals).
- There are reports of GM crops growing wild
away from their original fields of cultivation.
- Although these escaped populations often die
out they may cross-pollinate either a wild or cultivated relative of
- Apparently GM oilseed rape is capable of
cross-pollinating with 8 wild relative varities.
- GM crops can swap genes with other GM crops.
- 6. Unintended consequences - all sorts
of unfortunate possibilities:
- Points 4. and 5. have considerable
implications e.g. if the transplanted genes from GM plants spread to other native plants,
we do not know what genotypes will be formed and what will be the resulting
phenotypes (gene expression)?
- If we produce a GM herbicide resistant plant,
what happens if the herbicide resistant gene enters the genome of a weed,
will a herbicide resistant weed evolve (a 'superweed'), that is even more
herbicide resistant than the crop! From an agricultural point of view, a bit
- By using GM plants we are introducing genes
into the natural environment, over which we might not have as much
control as we would like!
- There is concern about insect resistant crops
killing other 'non-target' insects that are important to the wider,
but still local, ecology e.g. communities of harmless insects
important to food chains involving other animals.
- Pollen from GM crops can be carried by the
wind and may be toxic to other insects, which might themselves, be
important pollinators of other crops and non-crop plants and wild
- Many GM crops are made to resistant to a
herbicide ('weed killer') called glyphosate (one commercial name is
- Many environmentalists/ecologist believe this
herbicide is causing harm to some animals and plants.
- There is some evidence that it can harm
humans (e.g. cancer, autism), but again, its effects are disputed
- It is supposed to break down quickly in the
environment, after its killed he weeds, but ...?
- 7. There are
concerns about the welfare of
genetically engineered animals.
- You can't accurately predict all the effects
on an animal after its genome has been modified - you may produce
one desired product, but are there other genetic consequences?
- Many genetically modified embryos do not
survive, and genetically modified animals, especially clones, can
suffer from health issues.
- 8. Other aspects of producing GM foods
- Lack of a farmer's independence.
- If you use GM crops you cannot collect and
sow the seed, because it will not breed true.
- The farmer is forced to buy more seeds from
the farming company supplier.
- Therefore the seed companies can be perceived
as exploiting poorer farmers.
- 9. The marketing of GM foods
- Food companies should always have to
clearly label foods that contain GM products.
- That gives the consumer the rightful choice
as to whether the do, or do not, buy and eat genetically modified
- Further to this point, it is up to food
manufacturers to ensure that supposedly non-GM food is NOT
contaminated with GM ingredients.
- Not all food manufacturers will be ethical
about this and may try to substitute more expensive conventional
non-GM ingredients with less expensive GM products.!
developments - not good or bad?
- I've read that US scientists have engineered
a bacterium that need's an amino acid that does not occur in nature.
- If this bacteria escapes the culture
vessel, it cannot survive, since there is no natural source of
the amino acid.
- 11. Use of GM applications raises
issues in some peoples minds - a recap of where we started in
- Some people argue we are interfering with
nature and it is wrong to genetically modify organisms just for the
benefit of human beings AND uncertainty are the long-term
- Is it right to genetically engineer animals
just to benefits us, and ignoring their real/potential health
- Will we start genetically engineering our
offspring for a set of 'ideal' characteristics e.g. good looks,
intelligence, athletic prowess phenotypes etc.
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(g) Thoughts on
GM the world production of
See also more detailed
gcse biology revision notes
Food and the world's population
Lets start with some statistics - two graphs of population and energy
The graphs shows the acceleration of the world's population and therefore
and increasing food demand.
Although I have no data myself on the world's total food production,
but there are some graphs on ...
which clearly show a similar pattern in agricultural production.
BUT how long can this be sustained?, and there millions
(billions?) of undernourished people suffering from starvation and
disease, primarily from lack of local food production for one reason
or another e.g. climate conditions, war, overuse of soil using
non-sustainable agricultural practice.
To minimise the effects of lack of food, everyone should have access
to safe nutritious food - sufficient as well as providing a balanced
diet - this concept is known as 'food security'.
Food security can be defined as "the
state of having reliable access to a sufficient quantity of
affordable, nutritious food".
GM crops can help, but it is only one approach to increasing food production:
As already describe above, some developments so
genetically engineered crops can be designed to be pest
resistant and survive in drought conditions,
and crops can be GM designed to combat certain nutrient
deficiencies e.g. increasing the content of a chemical in
'Golden Rice' that helps make Vitamin A in the body.
However, there are still issue of concern
where GM is of little help:
Poor quality soil lacking in
nutrients or water means crops will fail, even if they are GM.
Though extra nutrients - fertiliser
can still be added to the soil.
Hunger exists where people
cannot afford to buy food, even if it is available,
therefore you need political and economic strategies to tackle
poverty and improve/make fairer the economy and maybe import
There is a danger that the agricultural
production of a country might be too dominated by multinational
companies that manufacture the GM seeds.
Other methods of increasing food production
GM crops are not the complete answer and neither
should they always the 'first choice' in the future.
There are reason for lack of food which GM cannot
do little about e.g.
Poor soil can be improved by application of
fertilisers, but not overuse, which causes environmental problems.
You can control disease and insect infestation without using
GM crops and/or herbicides and pesticides.
You can use biological methods to control pests -
deploying other organisms to reduce pest numbers which can act as
predators or parasites.
These biological methods can be more sustainable
than chemical pesticides, so less harmful to the environment.
See also more detailed
gcse biology revision notes
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Typical learning objectives for this page
Know and understand that genes can also be transferred to the cells of animals, plants
or microorganisms at an early stage in their development so that they
develop with desired characteristics.
Know that new genes can be transferred to crop
Crops that have had their genes modified in this way are called
genetically modified crops (GM crops).
Examples of genetically modified
crops include ones that are resistant to insect attack, viruses, fungi or to herbicides.
This is all about increasing the
quantity and quality of crops - insert genes into the plant's genome to
increase the size and the quality of the grain.
Large quantities of crops are
lost to disease and insect attack, so it make economic sense in principle.
One practical example is that if
you can make a crop resistant to a herbicide that is used to kill weeds -
weeds that compete for the soil nutrients, then you can kill the weeds
by spraying without damaging the crops.
You can produce plants (fruit or grain)
that are also resistant to diseases and insect attack to improve crop yields.
You can genetically engineer sheep to
produce substances like drugs in their milk, which are used to treat certain
Genetically modified crops generally show increased yields.
about GM crops include the effect on populations of wild flowers and
insects, and uncertainty about the effects of eating GM crops on human
There is considerable public
concern about GM crops eg are they harmful, are they as nutritious, are they
reducing biodiversity, will they spread and multiply at the expense of
native plants - out-compete for nutrients, will they cross-bread with native
plants changing the gene pool,
GM crops of rice, and other
basic grown foods, are seen as an economic way of feeding the growing poor
populations of third world countries.
The idea behind GM crops is to
increase yields and increase nutrition.
You can insert genes into crop
cells so that they contain particular nutrients, whose deficiency can cause
ill-health, or engineer a strain of wheat to contain more protein if meat is
So there are lots of
possibilities and lots of controversies - so 'watch this GM space'
- In the context of genetic engineering, be able to explain the role of the scientific
community in validating new evidence, including the use of:
- a) scientific journals - enable new findings
on genetic engineering to be communicated to other scientists working in the same areas of science,
so ideas and knowledge are widely spread AND other scientists can check
whether the research is valid eg do other scientists get the same results?
do other scientists draw the same conclusions? do other scientists agree
with, and find the theory valid?
- b) the peer review process - a sort of
refereeing system, research papers on genetic engineering are read and checked by people competent
to understand the contents of research papers (their peers) - this ensures
standards are high in terms of 'good scientific practice'.
- c) scientific conferences enable scientists to
meet and present and discuss their findings on genetic engineering, compare their work, listen to
new ideas, get ideas to take back to their own research project. Its also a
forum for other scientists to hear about research which isn't necessarily
exactly their own specialist field, but broadens their own knowledge of
related fields of science e.g. genetic engineering.
Be able to make
informed judgements about the social and ethical issues concerning the use
of stem cells from embryos in medical research and treatments
Be able to make
informed judgements about the economic, social and ethical issues concerning
Be able to demonstrate an understanding of how gene
mutations change the DNA base sequence and that mutations can be:
(i) harmful - causing genetic disorders like
cystic fibrosis, Downe syndrome, haemophilia and colour blindness.
(ii) beneficial - the gene expression
produces an enhanced feature that makes that organism more able to survive,
this is partly responsible for driving the evolution of more successful
species, but not always to our benefit! e.g. bacteria genes are quite
susceptible to mutations and some are becoming very resistant to antibiotics
as their DNA subtly changes!
(iii) or neither ('neutral') - any faults
from DNA mutations do not affect the organisms existence i.e. protein
functions are not affected, no advantage is gained and no disadvantage
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