**7.1 Molecular analysis**

GM crops can be tested by several molecular levels such as at DNA, mRNA and protein level. Polymerase Chain Reaction (PCR) is the primary method for screening of GM crops at DNA level. This method has found very broad and wide applications in GMO detection and in this method target gene multiplied to millions or billions by using gene specific primers [30]. Southern blotting is another important method for the identification of specific DNA fragments transformed into the genome of transgenic plants or its products which was described by Southern in 1975 [31]. This is very reliable method that provides the molecular evidence of the transgene integration and also estimates the copy number of introduced gene into the host genome. DNA microarray is another method used to identify the expression of more than one gene in a single test. This test method has been used in GMO screening as a method for simultaneous detection of more than 250,000 targets in single assay/chip [32]. In case of RNA based methods real-time PCR, northern blotting techniques etc. are used to monitor and study the gene expression in GM crops. RT-PCR method is based on reverse transcription of mRNA and synthesis of complementary DNA (cDNA) which is then used as template in PCR amplification of target gene. In real-time assay of transgene in GMOs, the amplification and detection occur simultaneously [33]. In northern blotting also requires mRNA as tested material from GMOs. This is a standard method for the analysis of size and level of target RNA in a complex GMO sample. It gives comparative amount of gene expression at the RNA level. Protein based test methods enzyme linked immune sorbent assay (ELISA) and western blot methods have been used for the protein analysis in GMOs. In this assay protein specific antibody coated multi-well plate is used to identify and quantify the specific protein [34].
