Transcript PowerPoint 簡報

Genetically
Modified foods
By 7B Chau Shuk Tak
WHAT IS GM FOOD?
Individual characteristics of plants, such as the height
to which wheat grows or the colour of petals, are
determined by their genes. These characteristics, or
traits, are inherited from generation to generation.
Genetic modification (GM) involves copying the genes
which govern a particular characteristic from one
organism, and transferring them to another.
WHAT ARE THE DIFFERENCES BETWEEN
CONVENTIONAL BREEDING AND GENETIC
MODIFICATION ?
Conventional breeding
Genetic modification
With conventional breeding,
traits can only be transferred
between plants or animals of
the same or closely related
species.
GM enables traits to be
transferred between different
species, and potentially even
between animals and plants
This method requires a lot of
effort and is rather imprecise.
Genetic modification is
quite precise
Conventional breeding
Genetic modification
Breeding does not introduce
new genetic material into the
gene pool of the species but
merely selects and brings
together in one individual
certain genes that are already
in the gene pool.
The method introduces
new genetic material into
gene pool, for example
fish gene is inserted into
tomato.
Examples of GM food
Maize genetically
modified to Bt
protein
maize
Maize
Maize
Maize
Maizegenetically
geneticallymodified
modifiedto
toproduce
produce
Bt
Btprotein
protein
Bt protein kills
corn borer
insect
Bt
Btprotein
proteinkills
killsthe
the
corn
cornborer
borer insect
insect
‘Bt maize’ has been genetically modified to make it produce a protein from
the bacterium Bacillus thuringiensis. This protein kills the corn borer insect
which, in other countries, is a major threat to maize crops.
How to add a fish gene to a tomato?
Scientists have created a frost-resistant tomato plant by adding an
antifreeze gene from a cold-water fish to it. The antifreeze gene
comes from the cold-water flounder, a fish that can survive in very
cold conditions. This is how it was done.
The antifreeze DNA is joined onto a piece
of DNA called a plasmid. This hybrid DNA,
which is a combination of DNA from 2
different sources, is known as
recombinant DNA.
The recombinant DNA, including the antifreeze gene, is
placed in a bacterium.
The bacterium is allowed to reproduce many
times producing lots of copies of the recombinant
DNA.
Tomato plant cells are infected with the bacteria.
As a result, the antifreeze gene in the plasmid, in
the bacteria becomes integrated into the tomato
plant cell DNA.
Tomato cells are placed in a growth medium that
encourages the cells to grow into plants.
Tomato plant seedling is planted.
This GM tomato plant contains a copy of the flounder antifreeze
gene in every one of its cells. The plant is tested to see if the
fish gene still works. Is it frost resistant? Yes it is.
What are the benefits of GM food?
Increased Yields
Making crops resistant to insects and diseases and
reducing weeds should lead to fewer crop losses. The
global area of GM crops has increased 30-fold in six years.
Fewer Pesticides Used
Insect resistant crops can lead to significant reductions in the use of
insecticides. Corn borers enter the maize stalk and eat the plant from
the inside. GM maize protects itself against the corn borer and
usually only one application of insecticide is needed to control other
pests
Reduced Soil Erosion
With non-GM Soya, weeds are cleared before seeds are planted.
With herbicide tolerant Soya this is not necessary as the weeds
can more easily be controlled at a later stage. GM seeds are
planted by placing them directly into relatively undisturbed soil.
This conserves moisture and soil fauna and flora, and reduces
water and wind erosion.
Feed the world
With the global population expected to rise to 9 billion
within 50 years, feeding the world has never seemed such
a daunting task. But GM technology is giving hope to
developing countries, where many people think
biotechnology can offer improved nutrition, health and
prosperity.
What are the risks of GM food?
Allergy alert
In 1997, US scientists inserted a gene from a Brazil nut into
soybeans to make them more nutritious. But the gene also
passed on the property of nuts that causes allergies in people.
Also, A brand of BT corn was found to express a toxin that
scientists thought might cause allergies because of its molecular
structure.
Attack of the super bugs
BT crops that produce their own insecticide could create
populations of super bugs - pests that are resistant to
the toxins produced by these GM crops.
Possible loss of beneficial insects
Bt toxin will travel through the food chain and kill beneficial
insects such as lacewings and ladybirds. Another concern is that
if GM crops are more effective at killing target insects this might
deprive other organisms which prey on them, such as birds. The
Bt toxin will travel through the food chain and kill beneficial insects such as lacewings and ladybirds. Another concern is that if GM crops are
beneficial
insects
byasGM
crops
morepotential
effective at killing harm
target insectsto
this might
deprive other organisms
whichcaused
prey on them, such
birds. The
potential is
harmbeing
to beneficial
insects
caused
by
GM
crops
is
being
further
researched.
further researched.
Runner genes
Environmentalists are worried that GM crops could pollinate wild
plant species, introducing foreign GM genes into non-GM species.
This could transfer herbicide resistance to weeds, making them
difficult to wipe out.
Could genes put into GM crops cause the
next plague?
When people are infected by a population of antibioticresistant bacteria, the infection can become impossible to
treat. This has sparked fears of new plagues caused by
resistance genes getting into the environment
use of broad spectrum herbicides which kill a wide range of plants will lead to a loss of biodiversity.
Loss of Biodiversity
Use of wide spectrum of herbicides which kills
wide range of plant lead to loss of biodiversity.
HOW TO DEAL WITH GM FOOD AS
CONSUMERS?
1.To know more about the truth and the recent condition,
environmental education is very important. Absorb more
information related to the environment, raise environmental
protection attitude and practice, only the change of attitude,
can help to keep a positive heart to against GM Food.
2. When people noticed about they had in-take some kind of GM
Food which is under the condition without their permission or
being noticed, a sound raised up by the consumer
organization around the world "force labeling all the GM
Food". For this labeling, it means consumers can boycott GM
Food which will cause uneconomical to produce this kind of
food. Label is very important for chasing the occurrence of
health problems. HK government is now considering the
labeling system of foreign countries, researching results will
be handed out and reported to the Legislative Council.
Reference
1. Pandora’s Picnic Basket ---The Potential and Hazards of
Genetically Modified Foods
2. www.bbc.uk.co/science/
3. www.foodfuture.org.uk/
4. http://resources.ed.gov.hk/