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GMO Investigator Kit
Is your food genetically modified?
GMO Workshop Time Line • Introduction to GM foods
• DNA extraction of food products
• Set up PCR reactions
• Electrophorese PCR products
• Analysis and interpretation of results
GMO Investigator
ProceduresOverview
What is a GMO?
"genetically modified organism (GMO)"
an organism in which the genetic material has been altered in a way that does not occur naturally by mating and/or natural recombination
US Approval for GM food crops
•Corn
•Soy
•Papaya•Canola
•Potato
•Chicory
•Rice
•Squash
•Sugarbeet
•Tomatoes
Approval does not necessarily mean these crops are distributed
Database of GM crops: www.agbios.com
Which foods contain GM product?
Which foods contain GM product?
0
10
20
30
40
50
60
70
80
90
100
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
% o
f a
ll c
rop
pla
nte
d GM corn GM soy
Sources: 1996-1999 Fernandez and McBride, 2000-2004:
USDA, National Agriculture Statistics Service, Acreage.
Soy-based protein drinks/powders
Potato chipsMeatballs and
burgers
containing soy protein
Soy flour
Wheat flourFriesPuffed corn snacksCorn meal
Cereal (egcornflakes)
PopcornFlavored tortilla chips
Corn bread mix
Salad dressingFried corn snacksTortilla chipsFresh papaya
OilVeggie burgersVeggie sausagesFresh corn
Very Difficult / Not Possible
Less ReliableReliableVery Reliable
Which foods yield viable plant DNA?
Why test for GMO’s?
•LegislationLegislationLegislationLegislation
–US: food labeled “GM-Free” <5% GM
–EU: food labeled “GM” if >1% GM
–Japan: food labeled “GM” if >5%
•ExportExportExportExport
•What about unlabeled food?What about unlabeled food?What about unlabeled food?What about unlabeled food?
How to test for GMOs
ELISA:
Test for presence of proteins expressed from genetic modifications
Pro: Quick, cheap, low tech
Con: Crop specific, protein stability
PCR:
Test for presence of inserted foreign DNA
Pro: ID different GM crops, DNA stability
Con: Expensive, timely
How to test for GMOs
Test for GMOs by PCR:
1. Grind food
2. Extract DNA from sample
3. Test sample DNA for viable plant DNA
4. Test sample DNA for genetic modifications
Kit Controls • Bio-Rad certified non-GMO food
–Verify PCR is not contaminated
• GMO positive control DNA
–Verify GMO-negative result is not due
to PCR reaction not working properly
• Primers to universal plant gene(Photosystem II)
–Verify viable DNA was extracted
Why amplify a
plant gene?
To confirm that viable DNA was extracted and that negative GM result
isn’t due to a non-viable template.
Use highly conserved chloroplast
gene from Photosystem II – part of the light reaction of photosynthesis.
Why use
CaMV 35S
and NOS?
CaMV 35S – Sequence for the
promoter of 35S transcript of the
Cauliflower mosaic virus.
Used because it functions in every plant cell
NOS- Sequence for nopaline
synthase terminator from soil
bacterium Agrobacterium tumefacians
Used because it evolved to be recognized in most plants
Laboratory Quick Guide
Extract DNA
from food
50 µl
Volumetric
Measurements
Why these steps?
•Grinding food to release DNA
•InstaGene chelates divalent ions (e.g.
Mg2+) necessary for DNA degrading
enzymes (e.g. DNases)
•Only 50 µl of food transferred otherwise
InstaGene is overwhelmed (~ 5 mg of
original material)
•Boiling releases DNA from food into the
InstaGene solution
•Pellet InstaGene and food debris because
InstaGene inhibits PCR reaction (Taq needs
Mg++)
Mg++
Mg++
Mg++
Mg++
Mg++Mg++
Mg++
Mg++
InstaGene
Set up PCR
reactions
The PCR Reaction
What do you need?
What is needed for PCR?
• Template - the DNA to be amplified
• Primers - 2 short specific pieces of DNA whose sequence flanks the target sequence
�Forward
Reverse
• Nucleotides - dATP, dCTP, dGTP, dTTP
• Magnesium chloride - enzyme cofactor
• Buffer - maintains pH & contains salt
• Taq DNA polymerase – thermophillicenzyme from hot springs
Polymerase Chain Reaction
PCR Animationhttp://www.bio-rad.com/LifeScience/jobs/2004/04-0522/04-0522_PV92_PCR.html
The PCR Reaction
How does it work?
Heat (94oC) to denature DNA
strands
Cool (59oC) to anneal primers to
template
Warm (72oC) to activate Taq
polymerase, which extends primers
and replicates DNA
Repeat 40 cycles
Why have GM crops?
• Growing human population
• Loss of farmable land
• Remediation of soil
• Enrich nutrient content
Desirable Traits • Pest Resistance
• Herbicide Tolerance
• Viral Resistance
• Drought Resistance
• Increased Nutritional Value
• Improved Fruit
• Altered Ripening
Opponents argue
• Creation of super pests
• Creation of super weeds
• Loss of biodiversity
• Biotechnology companies
control agriculture
• Health concerns
Method for Genetic Modification of Crops
1. Choose desirable trait
2. Clone the gene
3. Engineer the gene
4. Transform gene into plant
5. Backcross GM plant into high yield crops
Choose desirable trait
•Pest Resistance: Bt crops
�Bacillus thuringiensis protein is a delta
endotoxin kills corn borers
•HerbicideTolerance: Round Up Ready crops
�Agrobacterium tumifaciens protein with
resistance to Round Up herbicide (glyphosate)
Bacillus thuringiensis
Delta endotoxin crystal
Clone the gene
Ti plasmidori
Bt gene
Bacillus thuringiensis
Delta endotoxin crystal
Ti genes
Engineer the gene
STOP
Antibiotic
resistance
Ti plasmidori
Bt gene
Ti genes
GO
Transform gene into plant
Isolate plant
cells
Grow
undifferentiated
callus
Transform cells
Select cells
Redifferentiate
callus
Grow
transgenic
plant
Backcross GM plant into high yield crops
GM plant =
yyGG
High yield plant =
YYgg
YYgg x yyGG YyGg
YYgg x YyGg
YYgG
YygG
YYggYygg
YYgG x YYgGYYgG
YYgg
YYGgYYGG
1 32 7654
GMO
positive
GMO
negative
1: non-GMO food with plant primers
2: non-GMO food with GMO primers
3. Test food with plant primers
4: Test food with GMO primers
5: GMO positive template with plant primers
6: GMO positive template with GMO primers
7: PCR MW Ruler
Analysis of
Results
1 32 7654
GMO Investigator Kit
Lab Extensions •Independent studies
•Data Mining/Bioinformatics for
specific genes
–E.g. Design primers to the cry genes in Bt corn
•Quantitative Real-Time PCR
Trouble shooting
• False PositivesFalse PositivesFalse PositivesFalse Positives
–Contamination-sterile technique; 10% bleach to clean pipette barrels, mortars & pestles, bench tops; barrier tips for all steps.
• False NegativesFalse NegativesFalse NegativesFalse Negatives
–No DNA extracted
–Possible food type or possibly primers do not work on that plant species
– InstaGene matrix transferred to PCR reactions
GMO Investigator Kit Contents
Not Included but required:
•Thermal cycler
•Water bath/heat block
•Electrophoresis Module
(agarose, TAE buffer & Fast
Blast DNA stain)
•Electrophoresis equipment
& power supply
•2-20 ul pipettes & barrier
tips
• Bio-Rad certified Non-GMO food
• InstaGene
• Master Mix
• GMO primers
• Plant PSII primers
• GMO & PSII positive control DNA
• PCR MW Ruler
• DPTPs, microtubes, PCR tubes, foam floats
• Manual