Genetic Engineering - techniques - splicing genes with enzymes!
uses e.g. making insulin, GM crops, medical applications
examples of biotechnology
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 do we mean by genetic engineering?
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
Be able to discuss the 'pros and cons'
of genetic engineering.
Note: GM is used as an abbreviation
for genetically modified products i.e. the produce of genetic engineering.
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.
The 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!
of genetically modifying a plants genome
for an enhanced characteristic
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.
The examples below
describe techniques used in agriculture to produce crops with desirable
characteristics that increase crop yields.
Scientists frequently used 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
A gene is taken from the cells of a herbicide
resistant plant and inserted into a plasmid extracted from the
Agrobacterium fumefaciens bacteria.
The genetically modified plasmid is inserted back
into the bacterium.
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 infect
the plant cells, modifying their DNA.
The modified plant cells can then be used to grow
mature plants with their newly acquired gene giving them the
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 reduces the use of insecticides, using less
insecticides is less damaging to ecosystems in the countryside.
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.
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
Other examples in brief
3. 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.
More on examples of the use of genetic engineering
Be able to discuss an understanding of the advantages and disadvantages of genetic
engineering to produce GM organisms, including:
- a) Increase the content of beta-carotene in golden rice
to reduce vitamin A deficiency in humans.
- 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 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.
- c) In 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!
- d) 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 resistant to certain 'pests' e.g. fungal attack or
- You can also make 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 survives!
- All of these effects will help to increase
the quality and yield of
- For more details see
Examples of genetically modifying
plants for an enhanced characteristic
- e) Medical researchers are trying to develop
genetic modification treatments for inherited diseases caused by faulty
- The idea is to insert correctly working genes
into people suffering from the disorder caused by faulty genes.
- This technique is called gene therapy.
- 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.
issues and 'pros and cons'
- 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?
- Will there be an increase in food allergies?
- 3. Are there any long-term effects 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 there be any effects on food chains and
- 4. Will GM plants spread and affect the
local diversity of the farmland and environs.
- 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?
- 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).
- 6. 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!
- 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. Use of GM applications raises ethical
issues in some peoples minds
- 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.
Thoughts on the world production of food
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.
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 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.
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