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GENETIC MODIFIED FOODGENETIC MODIFIED FOOD

Genetically Modified FoodGenetically Modified Food

Mechanism of Genetically Modified Mechanism of Genetically Modified Food--GM food (There are totally 2 Food--GM food (There are totally 2 methods)methods)

Applications of Genetic ModificationApplications of Genetic Modification Pros and Cons of GM foodPros and Cons of GM food NewsNews Government’s actionGovernment’s action

Mechanism of GM Mechanism of GM Food(1)Food(1)

1)Isolating/synthesizing the target 1)Isolating/synthesizing the target genegene

2)Inserting the target gene into a 2)Inserting the target gene into a vector, i.e. an intermediate carriervector, i.e. an intermediate carrier

3)Transferring the vector containing 3)Transferring the vector containing the target gene into a host cell and the target gene into a host cell and cloning the DNAcloning the DNA

5) Mixing plant cells with host cells5) Mixing plant cells with host cells

Mechanism1 : Isolating/synthesizing the Mechanism1 : Isolating/synthesizing the target genetarget gene

The ‘shotgun’ approach, using type II The ‘shotgun’ approach, using type II restriction enzyme(restriction endonrestriction enzyme(restriction endonuclease )uclease )

- the enzyme cuts at - the enzyme cuts at recognition sitesrecognition sites, to , to obtain a desired geneobtain a desired gene

- sticky ends or blunt ends produced (ther- sticky ends or blunt ends produced (there are figures later)e are figures later)

Making a copy of the gene from its mMaking a copy of the gene from its mRNA RNA

- - poly-T oligomerpoly-T oligomer binds to the complemenbinds to the complementary poly-A tail of the mRNAtary poly-A tail of the mRNA

- a single strand of - a single strand of DNA copy formedDNA copy formed - digesting - digesting mRNA mRNA - - a a double-stranded cDNA double-stranded cDNA produced produced

Sticky end and Sticky end and blunt endblunt end

Mechanism1 : Inserting the target Mechanism1 : Inserting the target gene into a vectorgene into a vector

Step 1) Prepare a target gene wiStep 1) Prepare a target gene with sticky end if it has blunt endth sticky end if it has blunt end

- - Short pieces of DNA are joined Short pieces of DNA are joined at the end of the geneat the end of the gene

- restriction enzyme- restriction enzymes cut linkerss cut linkers Step 2) Prepare the plasmid DNStep 2) Prepare the plasmid DN

A (a figure later) as vectorA (a figure later) as vector

- - centrifugationcentrifugation Step 3) Combine the target gene Step 3) Combine the target gene

and the plasmid DNA by DNA ligand the plasmid DNA by DNA ligasease

- To have the same sticky end, the same restriction enzyme is used to cut the vector

Plasmid DNAPlasmid DNA

Circular DNA(2), which is smaller and Circular DNA(2), which is smaller and lighter than main chromosomal DNA(1)lighter than main chromosomal DNA(1)

Mechanism1 : Transferring the vector Mechanism1 : Transferring the vector into a host cell (transformation) and into a host cell (transformation) and Cloning the DNACloning the DNA

Step 1) Adding the plasmid vector into a flask Step 1) Adding the plasmid vector into a flask containing culture of a host cellcontaining culture of a host cell

Step 2) Generating temporary pores on the Step 2) Generating temporary pores on the surface of the host cellsurface of the host cell

Step 3) Allowing the plasmid vector to enter Step 3) Allowing the plasmid vector to enter the host cellthe host cell

Step 4) Placing the host cell in a dish with Step 4) Placing the host cell in a dish with nutrientsnutrients

Mechanism1: Mixing plant cells Mechanism1: Mixing plant cells

with host cellswith host cells

Using Agrobacterium tumefUsing Agrobacterium tumefaciens or Agrobacterium rhaciens or Agrobacterium rhizogenes as vectorsizogenes as vectors

Introducing Ti-plasmid into Introducing Ti-plasmid into the plant cellsthe plant cells

The whole plant can be regThe whole plant can be regenerated from a transformeenerated from a transformed leaf discd leaf disc

Summary of the mechanism(1)

Mechanism of GM Mechanism of GM Food(2)Food(2)

Antisense approachAntisense approach Switching off or turning down (underexSwitching off or turning down (underex

pressing) a resident gene in the organispressing) a resident gene in the organismm

Antisense RNA is producedAntisense RNA is produced

Applications of Genetic Applications of Genetic Modification in Food Modification in Food

ProductionProduction GM FoodGM Food -Tomatoes and tomato paste -Tomatoes and tomato paste

-Corn maize -Corn maize

-GM soya beans -GM soya beans

GM processing aidGM processing aid -A kind of GM organism making a product without GM material-A kind of GM organism making a product without GM material

GM ingredients in animal feedGM ingredients in animal feed

Benefits of GM foodBenefits of GM food higher yieldshigher yields increased muscle bulk (animals)increased muscle bulk (animals) the ability to resist disease, pests or the ability to resist disease, pests or

chemicals chemicals a prolonged shelf-life a prolonged shelf-life higher nutritional value higher nutritional value reduced allergensreduced allergens the ability to grow in environments that the ability to grow in environments that

are usually too hostile.are usually too hostile.

Disadvantages of GM Disadvantages of GM foodfood

Unintended modification of similar species due to Unintended modification of similar species due to cross pollination cross pollination

Upsetting the ecosystem Upsetting the ecosystem Development of super pests Development of super pests Problems about religious, health, etc Problems about religious, health, etc Destroying the normal farming system Destroying the normal farming system Interfering the normal DNA system Interfering the normal DNA system Widening the financial gaps between developed and Widening the financial gaps between developed and

developing countries developing countries

News about GM News about GM food food

SOURCES: New Scientist (issue 2530) SOURCES: New Scientist (issue 2530)

Letter to the Editor, 17 December 2005Letter to the Editor, 17 December 2005

allergenic potential of genetically modified foods allergenic potential of genetically modified foods (e.g. mouse strains in peas )(e.g. mouse strains in peas )

Existing tests provide no direct immunological Existing tests provide no direct immunological information and cannot rule information and cannot rule

out allergenic proteins out allergenic proteins regulators should demandregulators should demand

full sequencing of the full sequencing of the

transgenic proteins in plants transgenic proteins in plants

SOURCES: ISIS Press Release 16December,2005SOURCES: ISIS Press Release 16December,2005

Genetically modified DNA from any part of a GM Genetically modified DNA from any part of a GM plant can enter the environment unobserved plant can enter the environment unobserved

causing a wave of “superweeds” causing a wave of “superweeds” ‘‘co-existence’ is biologically co-existence’ is biologically

impossible impossible

no existing public records of contamination incidents or other no existing public records of contamination incidents or other problems associated with GM crops problems associated with GM crops

strict rules with liability regulations should be applied by strict rules with liability regulations should be applied by governments to stop the governments to stop the

unauthorized spread of unauthorized spread of GM seeds and products GM seeds and products

data used by the data used by the Government to approve Government to approve GM foods should be GM foods should be accessed freelyaccessed freely

SOURCES: BBC News 8 December 2005SOURCES: BBC News 8 December 2005

Modified animals: 27%(2003) 32%(200Modified animals: 27%(2003) 32%(2004)4)

Total experiments: just over 2.85 million Total experiments: just over 2.85 million Number of animals used in research: 2.7Number of animals used in research: 2.7

8 million (a rise of 2.1% on 2003 figures)8 million (a rise of 2.1% on 2003 figures)

SOURCES: GM Free Cymru [Wales] SOURCES: GM Free Cymru [Wales] Press Notice 25thNovember 2005Press Notice 25thNovember 2005

Within three weeks of birth, Within three weeks of birth, - 55% of the rats fed on GM soya died - 55% of the rats fed on GM soya died - 9% of the rats died in the control group- 9% of the rats died in the control group mice fed on GM soya experienced a slowdown in mice fed on GM soya experienced a slowdown in

cellular metabolism and modifications to liver and cellular metabolism and modifications to liver and pancreaspancreas

introduction of genes from a bean variety into a Gintroduction of genes from a bean variety into a GM pea led to the creation M pea led to the creation

of a novel protein which of a novel protein which caused inflammation of caused inflammation of the lung tissue of mice. the lung tissue of mice.

What should HK What should HK governmentgovernment do? do? Setting up mandatory labelling system for Setting up mandatory labelling system for

GM foodGM food informing the public the pros and cons of informing the public the pros and cons of

GM foods GM foods building up its own expertise with public hbuilding up its own expertise with public h

ealth professionals and GM food-related ealth professionals and GM food-related scientists scientists

What did China What did China governmentgovernment do? do?

On March 20th 2002 , the Regulations on On March 20th 2002 , the Regulations on the Administration of the Safety of the Administration of the Safety of Transgenic Agricultural Products Transgenic Agricultural Products (RASTAP) became effective(RASTAP) became effective

According to RASTAP and its measures, According to RASTAP and its measures, two methods of application are required two methods of application are required to control the safety of transgenic to control the safety of transgenic products in international trade. products in international trade.

Regulations on the Regulations on the Administration of the Safety of Administration of the Safety of

Transgenic Agricultural Transgenic Agricultural Products (RASTAP)Products (RASTAP)

First, Chinese importers or foreign First, Chinese importers or foreign exporters must apply for the transgenic exporters must apply for the transgenic products which may be imported later to products which may be imported later to be risk assessed. be risk assessed.

Second, foreign exporters must label their Second, foreign exporters must label their transgenic products. transgenic products.