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What are GMOs?
Some technical background on the
genetic modification of plants
Stuart Brown
Associate Professor
NYU School of Medicine
Genetically Modified Organism
• The term GMO stands for Genetically
Modified Organism.
• Taken literally, this becomes meaningless,
since all organisms are in some sense
genetically modified – by natural evolution
and in agriculture by human selection.
(more on this in a minute)
• In current usage, GMO is applied to organisms
modified by recombinant DNA technology
DNA Ligase
Transgenic Plants
• Technologies have been developed to
permanently insert new genes into the DNA of
plants.
– Use of Agrobacterium which has the ability to insert
its DNA into plant cells
– Use of a “DNA gun” which blasts tiny particles coated
with DNA into plant cells
• Allows researchers to insert any gene into a plant
without requiring plant breeding, adding the
ability for the plant to make a new protein (or
RNA) molecule.
• GMO food animals are also possible, but not yet in
wide production
Gene Knock-out
• Sometimes the desired change is to block the
function of a gene that is in the plant – to stop
the production of a harmful product, or stop a
natural process
– Slow the ripening of tomatoes
– Block the browning of apples
– Remove harmful acrylamides from potatoes
• There are several ways to knock-out a gene with
DNA technologies
– Edit out the gene from the DNA
– Insert a blocking gene
CRISPR is a very new technology (2-3 years)
that allows more precise gene knock out and
replacement.
Tissue Culture
• Genetic modification of plants is done to single cells.
• It is then necessary to grow the modified cells back
into whole plants by tissue culture
• Tissue culture is a very common technique in standard plant production.
• Almost all commercial orchids are grown by tissue culture.
GMO Plant
• A specific plant variety that has
had a new gene inserted (or a
gene deleted) by genetic engineering methods
• May produces a new protein, not usually
found in that plant
• May have some other bits of DNA, and
possibly extra proteins from the engineering
process (parts of the cloning vector and the
selectable marker)
What Genes can be Added?
– Resistance to pests & disease (insects, fungi, viruses)
• Bt toxin against insects (Bt is naturally produced by bacteria)
• Virus resistant papaya
• Mildew resistant potato
– Tolerance to herbicides
• “Roundup Ready” soybeans & corn from Monsanto
– Change in plant growth and composition
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Slow ripening tomato (better transport and shelf life)
Non-browning apple
Low acrylamide potato
High Vitamin A rice (“Golden Rice”)
Are GMO Plants Safe?
• How to define “Safe” ???
• In the US we have food safety definitions which
are established and enforced by the FDA, EPA and
the Dept. of Agriculture.
• Europe has its own European Food Safety
Authority
• These definitions work reasonably well – none of
us in this room has been killed yet by USDA
approved foods.
– However there are many known food safety issues with
‘ordinary’ foods such as bacteria, mold, natural toxins,
allergies (many food recalls and restaurant scandals: JackIn-The-Box, Chipotle, etc.)
What are the Risks?
• Toxicity or allergy from the inserted protein(s)
• Toxicity or allergy from the other bits of DNA
that are added in the engineering process (the
vector and the selectable marker)
• Mutations that may occur during the
engineering and tissue culture process
How are GMO Plants Tested?
• GMO crops and foods are regulated under laws created
for invasive plants, chemical pesticides, and food
additives.
• Nearly all testing of GMO crops is done by seed and
biotech companies themselves, and evaluated by the EPA
and FDA.
• Very little testing of GMO food safety has been published
in peer-reviewed scientific journals.
• Scientific oversight of US Government regulation has
been provided by the US National Academy of Sciences:
Committee on Identifying and Assessing Unintended
Effects of Genetically Engineered Foods on Human Health
FDA Oversight
As of December 2012, the FDA has completed 95 consultations
“The foods evaluated through the consultation process have not been found to
be more likely to cause an allergic or toxic reaction than foods from traditionally
bred plants.”
Updated: 06/22/2015
What about “Traditional”
Plant Breeding?
• Humans have bred and selected plant varieties
for many thousands of years
• Current approved “natural” plant breeding
techniques include:
– Hybridization between distantly related plants
– Tissue culture
– Mutagenesis
• These methods can introduce large numbers of
new genes or random genetic changes to food
varieties
• New varieties produced by these methods are
not required to undergo any safety testing.
No Harm
• In the US, GMO foods have been approved and in
wide production for about 18 years.
• In that time not a single person has been made sick
by eating these GMO foods.
• Not a single lawsuit has been tried against GMO food
producers for harm to a person by eating GMO food
(not even in New York!!)
“Foods derived from GM crops have been consumed by hundreds of
millions of people across the world for more than 15 years, with no
reported ill effects.” – Journal of the Royal Society of Medicine
2008 Jun;101(6):290-8. doi: 10.1258/jrsm.2008.070372