Contents - Faperta

466 Biotechnological Approaches for Pest Management and Ecological Sustainability
Quantifi cation: If a crop or its product has been shown to contain genetically modifi
ed material, then it becomes necessary to assess the amount of each genetically
modifi ed variety or the transgene product present. Normally, quantifi cation is performed
using real-time PCR.
Sampling for Detection of Genetically Modified Food
One of the major considerations in analytical testing of almost any transgenic crop or its
product is the sampling procedure. The sample analyzed must be representative of the
material from which the sample is derived; otherwise, the testing regime becomes fl awed.
Sample preparation for both DNA-based and protein-based methods is critical for detection
and/or quantifi cation. It is important to know the limitations of each procedure, as
well as the purpose of detection. Both the sample size and sampling procedures dramatically
impact the conclusions that may be drawn from any of the testing methods. The fi rst
step is to collect a sample for analysis, which should be representative of the materials to
be analyzed. The sample should then be homogenized for isolation and purifi cation of RNA,
DNA, or protein. The quality, purity, and amount of DNA, RNA, or protein are important
for quantifi cation and detection. Variance associated with sampling is the most likely factor
to infl uence estimates of the proportion of genetically modifi ed material present in food
and food products. The sampling strategies should take into account the nature of the
analyte/foodstuff, and distribution of the analyte in the bulk food. The main parameters
to be taken into account should include lot size and uniformity, accepted testing methods,
and the preparation of the sample prior to analysis (Paoletti et al., 2003).
Detection of Genetically Modified Foods
Foods derived from genetically modifi ed plants are now appearing in the market and
many more are likely to emerge in the future. The safety, regulation, and labeling of these
foods are still contentious issues in most countries and recent surveys highlight consumer
concerns about the safety and labeling of genetically modifi ed foods. In most countries,
it is necessary to obtain approval for the use of genetically manipulated organisms in
food production (MacCormick et al., 1998). In order to implement the regulations governing
the production and marketing of food derived from genetically modifi ed organisms,
there is a need to develop and standardize technology to detect such foods. In addition, a
requirement to label approved genetically modifi ed food would necessitate a constant
monitoring system. One solution is to “tag” approved genetically modifi ed food from
transgenic plants with some form of biological or genetic marker, permitting the surveillance
of foods for the presence of approved products of genetic engineering. While genetically
modifi ed transgenic plants that are not approved would not be detected by such
surveillance, they might be detected by a screen for DNA sequences common to all or
most modifi ed transgenic plants.
Identifi cation of vector sequences, plant transcription terminators, and marker genes
by PCR and hybridization techniques can be used to detect the presence of genetically