GMO food/feed testing is based on some fundamental principles of genetic engineering and cellular physiology:
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DNA: The introduction of foreign DNA into a recipient plant’s DNA (genetic engineering)
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Protein: The information coded in DNA is translated into protein that performs the function specified by the DNA instructions (cellular physiology)
Two methods have been developed based on these fundamentals: genetic analysis (DNA analysis) and Immunological analysis (Protein analysis). Three tests are currently available using these methods.
Genetic Analysis (DNA analysis)
Genetic analysis is a GMO testing method that detects the presence of a transgene in a plant cell’s genome. The specific GMO test used in this method is called the polymerase chain reaction (PCR) test.
Polymerase Chain Reaction (PCR Test):
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Copies a specific section of a plant’s DNA billions of times in order to
detect and quantitate foreign DNA (GMO) inserted into the plant’s genome.
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Uses short pieces of DNA (primers) that are complementary to the GMO sequence to vastly amplify and quantitate GMOs.
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Performed in a laboratory setting.
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Appropriate for qualitative or quantitative testing.
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Highly sensitive and specific.
Immuno-analysis (Protein analysis)
Immunological analysis, or immuno-analysis for short, is a GMO test method that detects proteins. Currently, there are two types of GMO tests that use this method: the Strip Test and ELISA Method.
Strip test (Lateral Flow Device or Dipstick):
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A rapid antibody-based method used for measuring GMO protein in unprocessed material such as seed, grain, or leaves
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Uses a detection surface comprised of immobilized GMO protein-specific antibodies on a solid strip
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Appropriate for qualitative or semi-quantitative testing
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Suitable for field testing
ELISA Test (Enzyme-Linked Immunosorbent Assay)
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An antibody-based method for measuring GMO protein in unprocessed
material such as seed, grain, or leaves
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Uses a detection surface comprised of immobilized GMO protein-specific antibodies in a multi-well solid plate format
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Appropriate for qualitative or quantitative testing
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Performed in a laboratory setting
More on Immuno-analysis
Determining which type of GMO test is most appropriate depends on several factors, including but not limited to:
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Nature of the sample
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GMO(s) to be analyzed
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Required test sensitivity
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Whether qualitative or quantitative analysis is required
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Product’s intended market
The chart below summarizes GMO testing options, including the advantages and disadvantages of each method.
GMO testing options
|
Analysis |
Test |
Measures |
Advantages |
Disadvantages |
|
Immunologic |
Strip
test
|
Protein |
Because the test is rapid
and can be performed on-
site, this method is very
useful as an initial screen
for seed and grain |
Often low sensitivity (Limit of
detection 0.1 – 1%) |
Because the test is not
performed with laboratory
controls, operator error
resulting in inaccurate test
results can sometimes be an
issue. |
Not appropriate for processed
products |
GM protein levels may vary
between different commercial
GM cultivars and different parts
of the same GM plant |
|
ELISA |
Protein |
High sensitivity
(Limit of detection 0.01 –
0.1%) |
Not appropriate for processed
products |
GM protein levels may vary
between different commercial
GM cultivars and different parts
of the same GM plant |
Must be performed in a
laboratory |
|
Genetic |
PCR |
DNA |
High sensitivity (limit of
detection 0.01%) and
specificity |
Must be performed in a
laboratory |
Capable of detecting all
GMOs |
Allows definitive
quantification |
Effective with broad range
of sample types |
Industry standard used
worldwide in surveillance
and testing labs |