Genetic Engineering e.g. making insulin
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.
Know and understand in genetic engineering, genes
from the chromosomes of humans and other organisms can be ‘cut out’ using
enzymes and transferred to cells of other organisms.
- Be able to demonstrate an understanding of the
process of genetic engineering, including the removal of a gene from the DNA of one
organism and the insertion of that gene into the DNA of another organism
- This is exemplified by the production of
insulin from bacteria by inserting the human insulin gene into bacteria and
growing the bacteria to produce lots of insulin quickly and economically
This amounts to changing the
characteristics of an organism by changing its genes.
Useful genes from organism A can
be inserted into organism B.
The desired useful gene
(carrying desired characteristic) is cut out and isolated from the source organism A's
chromosome by specific enzymes and inserted into a vector.
The vector is usually a virus or a
bacterial plasmid - a circular piece of DNA found in bacterial cells.
When the vector is introduced to the
target organism, the useful genes inserted into the cell.
Other enzymes are then used to
remove an 'undesired' gene from organism B, the one you want to modify.
Then, via other enzymes, the
desired transplanted gene can be inserted into organism B.
It is hoped one day to cure the
genetic disorder cystic fibrosis with gene therapy ie replacing faulty genes
with correctly functioning genes.
The principles of genetic
engineering are illustrated by the production of insulin from bacteria
- 1. An appropriate bacteria is selected that
will give a good yield of insulin.
- 2.The bacterial plasmids are extracted from
the bacteria - the plasmid acts as the vector.
- 3. A section of the plasmid DNA is cut by enzymes.
- 4. The human gene responsible for insulin
production is cut from the human chromosomal DNA with enzymes.
- 5. Other enzymes are used to insert
('splice') the insulin gene in to the bacterial plasmid DNA.
- 6. The modified plasmids are put back into
the bacteria cells.
- 7. The bacteria rapidly reproduce when grown
in a fermenter.
- 8. The insulin is extracted and the waste
bacterial cells destroyed.
- The insulin can be used to treat people with
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
without damaging the crops.
You can produce plants (fruit or grain)
that are also resistant to diseases and insect attack.
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'
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.
- Vitamin A deficiency is common in many Asian
and African countries and can cause blindness.
- Golden rice is 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.
- 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!).
- c) The production of herbicide-resistant crop
- You can modify the genetic make-up of plants
by inserting genes that resistant to certain 'pests' e.g. fungal attack.
- 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!
- Both of these effects will help to increase
- d) 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.
- 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.
- 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 grain or vegetables etc.?
- By changing an organism's genome, you can't
predict whether problems will emerge for future generations (crops
- 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 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 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 a group of herbicide resistant weeds evolves ('superweeds'), that are 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!
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Typical learning objectives for this page
- 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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