PRESS CONFERENCE
GENETIC MODIFIED FOOD
Genetically Modified Food
 Mechanism of Genetically Modified
Food--GM food (There are totally 2
methods)
 Applications of Genetic Modification
 Pros and Cons of GM food
 News
 Government’s action
Mechanism of GM Food(1)
 1)Isolating/synthesizing the target
gene
 2)Inserting the target gene into a
vector, i.e. an intermediate carrier
 3)Transferring the vector containing
the target gene into a host cell and
cloning the DNA
 5) Mixing plant cells with host cells
Mechanism1 : Isolating/synthesizing
the target gene
 The ‘shotgun’ approach, using
type II restriction
enzyme(restriction
endonuclease )
- the enzyme cuts at recognition
sites, to obtain a desired gene
- sticky ends or blunt ends
produced (there are figures later)
 Making a copy of the gene from
its mRNA
- poly-T oligomer binds to the
complementary poly-A tail of the
mRNA
- a single strand of DNA copy
formed
- digesting mRNA
- a double-stranded cDNA
produced
Sticky end and
blunt end
Mechanism1 : Inserting the target
gene into a vector
 Step 1) Prepare a target gene
with sticky end if it has blunt end
- Short pieces of DNA are joined
at the end of the gene
- restriction enzymes cut linkers
 Step 2) Prepare the plasmid
DNA (a figure later) as vector
- centrifugation
 Step 3) Combine the target gene
and the plasmid DNA by DNA
ligase
- To have the same sticky end,
the same restriction enzyme is
used to cut the vector
Plasmid DNA
 Circular DNA(2), which is smaller and
lighter than main chromosomal DNA(1)
Mechanism1 : Transferring the
vector into a host cell
(transformation) and Cloning the
DNA
 Step 1) Adding the plasmid vector into a flask
containing culture of a host cell
 Step 2) Generating temporary pores on the
surface of the host cell
 Step 3) Allowing the plasmid vector to enter
the host cell
 Step 4) Placing the host cell in a dish with
nutrients
Mechanism1: Mixing plant cells
with host cells
 Using Agrobacterium
tumefaciens or
Agrobacterium rhizogenes
as vectors
 Introducing Ti-plasmid into
the plant cells
 The whole plant can be
regenerated from a
transformed leaf disc
Summary of the
mechanism(1)
Mechanism of GM Food(2)
 Antisense approach
 Switching off or turning down
(underexpressing) a resident gene in the
organism
 Antisense RNA is produced
Applications of Genetic
Modification in Food
Production
 GM Food
-Tomatoes and tomato paste
-Corn maize
-GM soya beans
 GM processing aid
-A kind of GM organism making a product without GM material
 GM ingredients in animal feed
Benefits of GM food
 higher yields
 increased muscle bulk (animals)
 the ability to resist disease, pests or
chemicals
 a prolonged shelf-life
 higher nutritional value
 reduced allergens
 the ability to grow in environments that
are usually too hostile.
Disadvantages of GM food
 Unintended modification of similar species
due to cross pollination
 Upsetting the ecosystem
 Development of super pests
 Problems about religious, health, etc
 Destroying the normal farming system
 Interfering the normal DNA system
 Widening the financial gaps between
developed and developing countries
News about GM food
SOURCES: New Scientist (issue 2530)
Letter to the Editor, 17 December 2005
 allergenic potential of genetically modified foods
(e.g. mouse strains in peas )
 Existing tests provide no direct immunological
information and cannot rule
out allergenic proteins
 regulators should demand
full sequencing of the
transgenic proteins in plants
SOURCES: ISIS Press Release 16December,2005
 Genetically modified DNA from any part of a GM
plant can enter the environment unobserved
 causing a wave of “superweeds”
 ‘co-existence’ is biologically
impossible
 no existing public records of contamination
incidents or other problems associated with GM
crops
 strict rules with liability regulations should be
applied by governments to stop the
unauthorized spread of
GM seeds and products
 data used by the
Government to approve
GM foods should be
accessed freely
SOURCES: BBC News 8 December 2005
 Modified animals: 27%(2003)
32%(2004)
 Total experiments: just over 2.85 million
 Number of animals used in research:
2.78 million (a rise of 2.1% on 2003
figures)
SOURCES: GM Free Cymru [Wales]
Press Notice 25thNovember 2005
 Within three weeks of birth,
- 55% of the rats fed on GM soya died
- 9% of the rats died in the control group
 mice fed on GM soya experienced a slowdown in
cellular metabolism and modifications to liver and
pancreas
 introduction of genes from a bean variety into a
GM pea led to the creation
of a novel protein which
caused inflammation of
the lung tissue of mice.
What should HK government
do?
 Setting up mandatory labelling system for
GM food
 informing the public the pros and cons of
GM foods
 building up its own expertise with public
health professionals and GM food-related
scientists
What did China government
do?
 On March 20th 2002 , the Regulations on
the Administration of the Safety of
Transgenic Agricultural Products
(RASTAP) became effective
 According to RASTAP and its measures,
two methods of application are required
to control the safety of transgenic
products in international trade.
Regulations on the
Administration of the Safety of
Transgenic Agricultural Products
(RASTAP)
 First, Chinese importers or foreign
exporters must apply for the transgenic
products which may be imported later to
be risk assessed.
 Second, foreign exporters must label their
transgenic products.