| Abstrakt: |
Foodstuffs made by modern biotechnology are requiring for special control. Analytical methods used for these purposes are being constantly perfected. When choosing a strategy for the analysis, several factors have to be assessed: specificity, sensitivity, practically of the method and time efficiency. To date, the GMO testing methods are mainly based on the inserted DNA sequences and newly produced proteins in GMOs. Protein detection methods are based mainly on ELISA. The specific detection of a novel protein synthesized by gene introduced during transformation constitutes an alternative approach for the identification of GMO. The genetic modification is not always specifically directed at the production of a novel protein and does not always result in protein expression levels sufficient for detection purposes. In addition, some proteins may be expressed only in specific parts of the plant or expressed at different levels in distinct parts of plant. As DNA is a rather stable molecule relative to proteins, it is preferred target for any kind of sample. These methods are more sensitive and specific than protein detection methods. PCR-based test can be categorized into several levels of specificity. The least specific methods are commonly called "screening methods" and relate to target DNA elements, such as promoters and terminators that are present in many different GMOs. For routine screening purpose regulatory elements 35S promoter, derived from the Cauliflower Mosaic Virus and the NOS terminator, derived from the nopaline synthase gene of Agrobacterium tumefaciens, are used as target sequences. The second level is "gene-specific methods". These methods target a part of the DNA harbouring the active gene associated with the specific genetic modification. The highest specificity is seen when the target is the unique junction found at the integration locus between the inserted DNA and the recipient genome. These are called "event-specific methods". For a quantitative assessment of GMO the most promising is PCR with the detection of results on the real time-scale. This method has several advantages such as high sensitivity and specificity, little time of analyses, which are conducted in a closed test-tube without contamination environment of PCR products. The microarray technologies have been developed in the past few years. The main principle of the micro-array technology is miniaturization. Methods can be performed on a much larger scale in much smaller volumes. |
