Download document 2848309

National 4/5 Biology
Therapeutic uses of cells and
genetic engineering
What are we going to learn?
• What is genetic engineering?
• What are the stages and techniques
involved in genetic engineering?
• Describe examples where genetic
engineering is used
What is genetic engineering?
• Genetic information can be transferred from one cell to another
naturally. This is the basis of sexual reproduction in which genetic
information from a sperm cell is transferred to an egg cell during
fertilisation.
• Some bacterial species can transfer plasmids between them
naturally. Viruses carry genetic material into the cells of other
species. or by genetic engineering.
• In recent decades, scientists have discovered that genetic
information can be transferred artificially from cells of one species
to the cells of another completely different species using techniques
called genetic engineering.
This involves the removal of required genes from the chromosome of
one organism and their insertion into the chromosome of a completely
different organism, usually a bacteria.
The technique stems from discoveries made in the early 1970’s:
• Bacteria have genetic material in rings, one large chromosomal ring
and one or more smaller rings called plasmids.
• Plasmids move freely between bacterial cells naturally, carrying their
genes with them. This enables a bacterium to acquire completely
new characteristics.
• Enzymes were discovered which could ______ ______ and ______
DNA -- the genetic engineer’s “scissors and glue”.
Genetic engineering is when pieces of chromosome (DNA/genes)
are transferred from one organism to another
Material is often transferred to bacteria as their DNA is loose in
the cytoplasm, making it easy to modify. They also grow and
replicate quickly.
loose strand
of main DNA
plasmid
– small ring of
additional DNA
A new gene can be inserted into the plasmid and the
bacteria then produce the protein for which the gene codes.
The steps involved...
1. The required gene is located on the donor chromosome.
2. The gene is removed from the chromosome.
3. A plasmid is removed from a bacterium.
4. The plasmid is cut open.
5. The gene is inserted into the plasmid.
6. The genetically altered plasmid is inserted into a bacterium.
The altered bacterium is propagated in optimum growing conditions to
produce many identical cells that can be used as biochemical
“factories”.
Use steps 1-5 to add labels to your diagram
Use steps 6 and 7 to add labels to your
diagram
Advantage of using micro-organisms
e.g. bacteria
• Bacteria are commonly used because they can be grown quickly
and easily, often at low cost.
• Given suitable conditions, genetically modified (GM) bacteria
multiply at a rapid rate and manufacture large quantitites of a
useful product than can then be extracted, concentrated, purified
and put to use.
Problems with trying to genetically engineer
a human
• Isolated cells of an advanced multicellular
organism such as a human being are often
difficult to mass produce in culture.
Uses
Genetic engineering has been used for a
number of reasons by scientists including:
•
•
•
•
•
making medicines
making plants resistant to disease
glow-in-the-dark organisms and cells
an enviropig
the spider-goat.
This website lists 12 examples of genetic
engineering from around the world.
Video clips
• TWIG: Genetic Modification clip (2 mins 49
secs)
• Animal Farm Channel 4 (episodes 1 & 2
approx 50 mins each).
• Making Insulin
• Insulin is a hormone (made of protein) which controls the
levels of glucose (sugar) in the blood. Insulin is normally
made by cells in the pancreas. Without insulin, the
glucose in the blood is not taken up by the cells, which
need the sugar for energy. Instead the glucose builds up
the blood and the cells are essentially starved. A person
with type 1 diabetes does not make insulin so needs to
have insulin injected from another source to keep them
healthy (from the previous topic you should be able to
explain what is likely to be the cause of someone not
making a particular protein).
• Traditionally, in the days before genetic
engineering, people with diabetes were treated
with pig or beef insulin. While this did solve the
problem, it was not ideal. Some patients suffered
strong side effects when using animal-derived
insulin. Vegetarians would obviously prefer not
to be using a medication obtained from an
animal. In recent years, there has been an
increase in the number of patients with diabetes
– this means more insulin is required and would
mean using more and more animals.
• In the 1980′s, insulin was made using a
genetic engineering by taking a copy of
the insulin gene from a human cell and
putting it into a bacterial cell.
• This animation from ABPI goes through
the steps of insulin production using
bacterial cells.
• The insulin gene is cut from the human
chromosome and extracted using special
enzymes. A plasmid is isolated from a bacterial
cell and cut open using special enzymes. The
insulin gene is then inserted into the plasmid
and joined together using an enzyme called
ligase. The new plasmid now contains bacterial
information and also the information for making
human insulin. This plasmid can be referred to
as ‘recombinant DNA’ meaning it has been
genetically engineering and combined from
different sources.
• The newly engineered plasmid is now inserted
into a new bacterial cell. This cell is now
genetically modified. The genetically modified
bacterial cell is now left to grow, in a fermenter,
and in doing so it produces insulin. The insulin is
then extracted and purified so that it can be used
to treat the patient.
• This OU video also summarises the process
focussing on insulin production. It goes on to
look at what scientists hope to use genetic
engineering for in the future.
Future possibilities
So… where is this all going?
Some scientists are taking genetic engineering a
step further. Not content with moving genes
between organisms, scientists are now creating
genes from scratch – i.e. genes not even found
in nature – and creating brand new organisms.
Ethics: What do you think?