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What is genetic
engineering?
·
Genetic engineering, sometimes called genetic modification, is
the process of altering the DNA? in an
organism’s genome?.
·
This may mean changing one base pair? (A-T or C-G),
deleting a whole region of DNA, or introducing an additional copy of a gene?.
·
It may also mean extracting DNA from another organism’s genome
and combining it with the DNA of that individual.
·
Genetic engineering is used by scientists to enhance or modify
the characteristics of an individual organism.
·
Genetic engineering can be applied to any organism, from a virus? to a sheep.
·
For example, genetic engineering can be used to produce
plants that have a higher nutritional value or can tolerate exposure to
herbicides.
How does genetic
engineering work?
To help
explain the process of genetic engineering we have taken the example of
insulin, a protein? that helps regulate
the sugar levels in our blood.
·
Normally insulin? is produced
in the pancreas?, but in people
with type 1 diabetes? there is a
problem with insulin production.
·
People with diabetes therefore have to inject insulin to control
their blood sugar levels.
·
Genetic engineering has been used to produce a type of insulin,
very similar to our own, from yeast and bacteria? like E. coli?.
·
This genetically modified insulin, ‘Humulin’ was licensed for
human use in 1982.
The
genetic engineering process
1.
A small piece of circular DNA called a plasmid? is extracted
from the bacteria or yeast cell.
2.
A small section is then cut out of the circular plasmid by
restriction enzymes, ‘molecular scissors’.
3.
The gene for human insulin is inserted into the gap in the plasmid.
This plasmid is now genetically modified.
4.
The genetically modified plasmid is introduced into a new
bacteria or yeast cell.
5.
This cell then divides rapidly and starts making insulin.
6.
To create large amounts of the cells, the genetically modified
bacteria or yeast are grown in large fermentation vessels that contain all
the nutrients they need. The more the cells divide, the more insulin is
produced.
7.
When fermentation is complete, the mixture is filtered to
release the insulin.
8.
The insulin is then purified and packaged into bottles and
insulin pens for distribution to patients with diabetes.
What else is genetic engineering
used for?
·
The first genetically modified organism to be created was a
bacterium, in 1973.
·
In 1974, the same techniques were applied to mice.
·
In 1994 the first genetically modified foods were made
available.
·
Genetic engineering has a number of useful applications,
including scientific research, agriculture and technology.
·
In plants, genetic engineering has been applied to improve the
resilience, nutritional value and growth rate of crops such as potatoes,
tomatoes and rice.
·
In animals it has been used to develop sheep that produce a
therapeutic protein in their milk that can be used to treat cystic fibrosis, or
worms that glow in the dark to allow scientists to learn more about diseases
such as Alzheimer’s?.
Alzheimer’s
disease and the worm
·
The nematode worm, C. elegans, only has around 300
cells in its entire nervous system, making it a very simple model for studying
Alzheimer’s disease.
·
Also, due to the fact the worm is nearly transparent, when their
nerve cells are labelled with green fluorescent protein (GFP), it is possible
to watch the location and activity of various structures and proteins under the
microscope.
·
The genetic material of C. elegans can easily
be genetically modified to make the worm produce specific proteins the
researchers want to study.
·
In humans, the APP gene codes for a protein
associated with the amyloid plaques that are characteristic of people with
Alzheimer’s disease.
·
So, to study Alzheimer’s, the researchers genetically engineered
the nerve cells of the worm to contain the APP gene,
effectively giving it Alzheimer’s.
·
By tagging the APP protein produced in the worm with green
fluorescent protein it was possible to see that all the cells that made contact
with APP died as the worm got older.
·
The researchers were then able to monitor the progression of
Alzheimer’s disease in the worm and go on to apply their findings to
understanding the role of APP in humans with Alzheimer’s disease.
What
is a GMO?
GMOs are organisms
that have had their characteristics changed through the modification of their
DNA.
· GMO stands for genetically modified organism
Genetically modified (GM) organisms are organisms that have had
their genomes? changed in a
way that does not happen naturally.By changing an organism’s genome we can change its
characteristics.Any organism could be genetically modified, but laws restrict
the creation of genetically modified humans, and the production and
distribution of other GMOs is tightly regulated.Common examples of GMOs are GM crops used in agriculture and
GM model organisms? used in
medical research.
How do we make GMOs?
·
To create a GMO, we change specific characteristics by using lab
techniques to delete or alter particular sections of DNA?.
·
We can also change an organism’s characteristics by introducing
new pieces of DNA into their genomes. This could be:
o
DNA taken from the same species?
o
DNA taken from a different species
o
DNA made synthetically in the lab.
·
The process of creating GMOs is called genetic modification
or genetic engineering.
·
There are several techniques that can be used to modify a
genome:
o
'Agrobacterium-mediated' genetic modification is a technique
used to introduce new DNA into a plant genome using a modified microbe?.
o
'Gene targeting' is a technique used to introduce new DNA into
selected regions of a genome through a process called homologous
recombination?.
o
'Genome editing' is a technique used to change selected regions
of a genome using enzymes? designed to
cut specific DNA sequences?.
Why do we make GMOs?
·
GMOs are generally made for medical, environmental, or
commercial reasons.
o
GM white mushrooms have had a gene? that normally
causes them to go brown altered so it no longer functions. These mushrooms take
longer to go brown, prolonging their shelf-life.
o
GM bacteria? have been
developed that have had a gene for insulin? added to
their genome. These bacteria produce large quantities of insulin as they grow,
which is then extracted and used by people with diabetes? to control
their blood sugar levels.
o
The Acer1 gene is thought to be
involved in skin diseases like psoriasis. GM mice have been made where
the Acer1 gene no longer functions to study what it
normally does. These mice have hair loss and are less able to control
heat and water loss from their skin.
