Genetically Modified Foods:
Myths and Realities
Source:
Source: www.accessexcellence.org
www.accessexcellence.org
Miracle
Miracle foods
foods for
for aa hungry
hungry world.....
world.....
http://scope.educ.washington.edu/gmfood/
http://scope.educ.washington.edu/gmfood/
.....or
.....or public
public menace?
menace?
i.cnn.net/.../10/biotech.us.europe/story.gm.jpg
i.cnn.net/.../10/biotech.us.europe/story.gm.jpg
http://www.newint.org/issu
http://www.newint.org/issu
e320/Images/tradepic.jpg
e320/Images/tradepic.jpg
http://www.foeeurope.org/press/eric01.jpg
http://www.foeeurope.org/press/eric01.jpg
Questions:
What’s a GMO?
Are GMOs new?
Are GM foods safe to eat?
Are GM crops safe to grow?
Question: What’s a GMO?
⇒
⇒ A
A GMO
GMO is
is aa “genetically
“genetically modified
modified organism”
organism”
⇒
⇒ Today
Today this
this means
means aa crop
crop plant
plant with
with extra
extra genes
genes
Question: Are GMOs new?
⇒
⇒ GM
GM means
means “genetically
“genetically modified”
modified”
⇒
⇒ All
All human
human food
food crops
crops are
are genetically
genetically modified
modified
⇒
⇒ To
To survive
survive in
in the
the wild,
wild, plants
plants must
must scatter
scatter seeds
seeds
⇒
⇒ For
For people
people to
to harvest
harvest seeds,
seeds, they
they have
have to
to stick
stick
www.kukurydza.org.pl/images/teosinte1.jpg
www.kukurydza.org.pl/images/teosinte1.jpg
Corn: a “traditional” GMO
www.kukurydza.org.pl/images/teosinte1.jpg
www.kukurydza.org.pl/images/teosinte1.jpg
evolution.berkeley.edu/.../images/c
evolution.berkeley.edu/.../images/c
ornfld.jpg
ornfld.jpg
http://www.arini.ac.uk/pics/maize%202AltD.jpg
http://www.arini.ac.uk/pics/maize%202AltD.jpg
Familiar genetically modified foods
http://scope.educ.washington.edu/gmfood/
http://scope.educ.washington.edu/gmfood/
http://primera.tamu.edu/kcchome/homeowner/riored.htm
http://primera.tamu.edu/kcchome/homeowner/riored.htm
⇒
⇒ Today’s
Today’s GMO
GMO aa crop
crop plant
plant with
with extra
extra genes
genes
⇒
⇒ The
The extra
extra genes
genes were
were added
added using
using recombinant
recombinant
DNA
DNA techniques
techniques
⇒
⇒ Changing
Changing plants
plants with
with recombinant
recombinant DNA
DNA techniques
techniques
is
is called
called “genetic
“genetic engineering”
engineering”
Plasmid
Making
recombinant
DNA
Foreign DNA
DNA is cut
with EcoRI
Sticky ends
DNA ligase
Source:
Source: www.accessexcellence.org
www.accessexcellence.org
Source:
Source: www.accessexcellence.org
www.accessexcellence.org
Bacterial transformation
Antibiotic sensitive
bacterial cell
CaCl2 treatment
to permeabilize
cell walls
Selection on bacterial growth medium
containing appropriate antibiotic
Add plasmid DNA
“Transformed“ bacterial cell
Making many copies of the recombinant DNA
Agrobacterium: nature’s genetic engineer
Agrobacterium is the causative agent of galls
Introducing genes using the Ti plasmid
NEW GENE
Ti plasmid
T-DNA
Plant’s DNA
Agrobacterium
Nucleus
Plant cell
The new gene is integrated into the plant’s DNA
NEW GENE
Plant’s DNA
Nucleus
Plant cell
Here’s how it looks in the laboratory
A plant with a new gene added
Molecular methods in plant improvement
Today:
⇒ Insect resistant plants
⇒ Herbicide-tolerant plants
⇒ Virus resistant plants
⇒ Vitamin A- and iron-enriched rice
The story of papaya
ringspot virus
http://www.apsnet.org/educat
http://www.apsnet.org/educat
ion/feature/papaya/Top.htm
ion/feature/papaya/Top.htm
The story of papaya
ringspot virus
The story of papaya
ringspot virus
1980s:
1980s: PRSV-resistance
PRSV-resistance project
project starts
starts under
under direction
direction of
of Dennis
Dennis Gonsalves
Gonsalves
1991:
1991: First
First transgenic
transgenic PRSV-resistant
PRSV-resistant papaya
papaya plant
plant
1992:
1992: PRSV
PRSV discovered
discovered in
in Puna
Puna district
district
1992:
1992: First
First field
field trials
trials PRSV-resistant
PRSV-resistant papaya
papaya plants
plants
1994:
1994: USDA
USDA grants
grants permission
permission for
for large
large scale
scale field
field trials
trials
1995-97:
1995-97: Approvals
Approvals for
for release
release from
from USDA,
USDA, EPA,
EPA, FDA
FDA
1992-1997:
1992-1997: PRSV
PRSV takes
takes its
its toll;
toll; many
many farmers
farmers go
go out
out of
of business
business
1998:
1998: Seeds
Seeds released,
released, free
free of
of charge,
charge, to
to growers
growers
2000:
2000: Papaya
Papaya industry
industry bounces
bounces back;
back; crop
crop back
back to
to pre
pre 1995
1995 levels
levels
The story of papaya
ringspot virus
http://www.apsnet.org/education/feature/papaya/Top.htm
http://www.apsnet.org/education/feature/papaya/Top.htm
Bt corn
http://dragon.zoo.utoronto.ca/~jlm-gmf/T0201A/corn1.jpg
http://dragon.zoo.utoronto.ca/~jlm-gmf/T0201A/corn1.jpg
Fusarium
Fusarium ear
ear rot
rot produces
produces fumonisins
fumonisins
Kernel
Kernel rot
rot produces
produces aflatoxin
aflatoxin
http://www.apsnet.org/online/feature/BtCorn/Images/healthy%20ear.JPG
http://www.apsnet.org/online/feature/BtCorn/Images/healthy%20ear.JPG
Bt corn
http://dragon.zoo.utoronto.ca/~jlm-gmf/T0201A/corn1.jpg
http://dragon.zoo.utoronto.ca/~jlm-gmf/T0201A/corn1.jpg
Fusarium
Fusarium ear
ear rot
rot produces
produces fumonisins
fumonisins
Kernel
Kernel rot
rot produces
produces aflatoxin
aflatoxin
http://www.apsnet.org/online/feature/BtCorn/Images/healthy%20ear.JPG
http://www.apsnet.org/online/feature/BtCorn/Images/healthy%20ear.JPG
Molecular methods in plant improvement
Tomorrow: ⇒ Nutritionally enhanced crops
⇒ Anti-cancer substances
⇒ Edible vaccines
⇒ Antibodies from plants
⇒ Biodegradable plastics
⇒ New biomaterials
⇒ Disease-resistant plants
⇒ Spoilage-resistant seeds and tubers
⇒ Stress-resistant crops
⇒ High-yielding pseudo C44 rice
Golden rice
Rice with vitamin A and iron
Are GM foods safe to eat?
⇒ Is DNA safe to eat?
⇒ Could antibiotic genes get into people?
⇒ Could GM foods contain new toxins?
⇒ Could GM foods cause allergies?
Are GM foods safe to eat?
⇒ Is DNA safe to eat?
All foods contains DNA -- about a teaspoon of DNA in a pound of food
Adding one gene adds roughly 1 part in a million or ~0.0001%
DNA is digested starting in your mouth
Tiny fragments gets through the digestive process
This is always happening when we eat food
It doesn’t change our genes
Are GM foods safe to eat?
⇒ Could antibiotic resistance genes get into people?
No, DNA is broken down into tiny pieces in our digestive tracts
⇒ Could they get into other bacteria in the gut?
Bacteria take up DNA very rarely
Transfers to gut bacteria have been looked for, but not found
Are GM foods safe to eat?
⇒ Could GM foods contain new toxins?
Plants contain chemicals that are toxic -- in large amounts
The FDA requires chemical analyses and toxicity studies
GM foods are better analyzed than any in human history
Are GM foods safe to eat?
⇒ Could GM foods cause allergies?
⇒ Allergy facts
Most food allergies are caused by about half a dozen proteins
Foods contain more than 100,000 different proteins
The FDA requires developers to identify allergenicity potential
What’s the bottom line?
A GM food is less likely to cause a problem
than any new food you’ve ever tried
Are GM crops safe to grow?
⇒ Could genes escape from crops to cause problems?
⇒ Will GM crops reduce biodiversity?
⇒ Could genes escape from crops to cause problems?
Gene transfer from crops to other plants is now called “gene flow”
Gene flow occurs between members of the same species
Gene flow is not a new problem in agriculture
⇒ What kinds of problems does gene flow cause?
It depends on the crop
⇒ Will GM crops reduce biodiversity?
The monarch butterfly incident
Bt genes in Mexican land races
http://www.scu.edu/cas/research/images/smecology.jpg
http://www.scu.edu/cas/research/images/smecology.jpg
http://www.newsroom.ucr.edu/images/releases/997_0.jpg
http://www.newsroom.ucr.edu/images/releases/997_0.jpg
⇒ Will GM crops reduce biodiversity?
“Nothing has driven more species to extinction or caused more
instability in the world’s ecological systems than the development
of an agriculture sufficient to feed
feed 6.3
6.3 billion
billion people.”
people.”
“To assert that GM techniques are a threat to biodiversity is to state
the exact opposite of the truth.”
“The less focused and productive this agriculture is, the more
destructive its effects will be.”
Peter
Peter Raven,
Raven, Director
Director of
of the
the Missouri
Missouri Botanical
Botanical Garden
Garden
Why are attitudes toward GM foods so negative?
Does it matter whether we accept GM crops?
“You people in the developed world are certainly free to debate the
merits of genetically modified foods, but can we please eat first?”
-- Florence Wambugu, 2003