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Detection and Monitoring of Food and Food Products 467
modifi ed plant material in food and food products (Table 16.1). Detection methods can be
based on detection of DNA, RNA, or the transgene product associated with the genetic
modifi cation. The majority of the methods developed for detection of genetically modifi ed
products are based on DNA, while a few are based on RNA. The DNA can be purifi ed in
billions of copies while the multiplication of RNA or the protein is more complicated and
a slow process. The RNA and the protein molecules are also less stable. The relationship
between quantity of genetically modifi ed foods and DNA is linear if genetically modifi ed
DNA is nuclear, but there is no such correlation between the quantity of genetically modifi
ed food and the RNA or protein (Holst-Jensen, 2006). The most commonly used methods
are gel electrophoresis and hybridization techniques that allow the size and amount of
DNA to be estimated. This can be coupled with digestion of DNA with restriction enzymes
that are known to cut a PCR fragment into segments of specifi ed sizes. Determination of
melting point profi les, which is characteristic of a specifi c DNA sequence, can also be used
for detection of food derived from genetically modifi ed crops. Another alternative is to use
short synthetic molecules called probes (similar to, but smaller than primers) and allow
TABLE 16.1
Methods for Detection of Genetically Modifi ed Food and Food Products
Method Target Sequence References
Plant-derived DNA Chloroplast tRNALeu gene (trnL) intron Taberlet et al. (1991)
Specifi c plant species Maize single copy invertase (Ivr) gene Ehlers et al. (1997)
Soybean single copy lectin gene Meyer et al. (1996)
Tomato single copy polygalacturonase gene Busch et al. (1999)
Gene-specifi c methods Caulifl ower mosaic virus promoter (P-35S) Pietsch et al. (1997)
Nopaline synthase terminator (T-Nos) Pietsch et al. (1997)
Bar (phosphoinothricin acetyltransferase) gene Ehlers et al. (1997)
Synthetic cry1Ab gene Ehlers et al. (1997),
Vaitilingom et al. (1999)
Construct-specifi c Bt11 maize: junction alcohol dehydrogenase 1S Matsuoka et al. (2001)
methods
intron IVS6 (enhancer)—cry1Ab gene
Bt176 maize: junction CDPK (calcium dependent
protein-kinase) promoter—synthetic cry1Ab gene
Hupfer et al. (1998)
GA21 maize: OTP (enhancer)—epsps gene
(RoundupReady tolerance)
Matsuoka et al. (2001)
Mon810 maize: junction P-35S—heat shock protein
(hsp) 70 intron I (enhancer)
Zimmermann et al. (1998)
Mon810 maize: junction hsp 70 intron—cry1Ab gene Matsuoka et al. (2001)
RoundupReady ® : junction P-35S—Petunia hybrida
CTP (chloroplast transit peptide)
Wurz and Willmund (1997)
T25 maize: junction pat (phosphoinothricin
acetyltransferase) gene—T-35S
Matsuoka et al. (2001)
Zeneca tomato: junction T-Nos-truncated tomato
polygalacturonase gene
Busch et al. (1999)
Event-specifi c methods Bt11 maize: junction host plant genome—
Zimmermann, Luthy, and
integrated recombinant DNA
Pauli (2000)
Roundup Ready ® soybean: junction host plant Berdal and Holst-Jensen (2006),
genome—integrated recombinant DNA
Taverniers et al. (2001),
Terry and Harris (2001)