Detection Methods of GMOs
1. The importance of having detection methods
Laws and regulations on the labeling of genetic modified foods have been established by countries. In order to establish these regulations, detection methods are needed as it enables the government sectors to detect and quantify the GMOs in foods. In addition, it provides transparency to the public or consumers on the GMOs in the food.[1]
2. Types of detection methods
Most of analytical tests on the GMOs are targeting on the DNA and protein [1]. The commonly use DNA-based method for the GMOs detection is the Polymerase Chain Reaction (PCR).
PCR involves 4 steps
1. The importance of having detection methods
Laws and regulations on the labeling of genetic modified foods have been established by countries. In order to establish these regulations, detection methods are needed as it enables the government sectors to detect and quantify the GMOs in foods. In addition, it provides transparency to the public or consumers on the GMOs in the food.[1]
2. Types of detection methods
Most of analytical tests on the GMOs are targeting on the DNA and protein [1]. The commonly use DNA-based method for the GMOs detection is the Polymerase Chain Reaction (PCR).
PCR involves 4 steps
(1): Sampling and sample preparation
(2): DNA purification/ Isolation of DNA
(3): PCR amplification and detection of reaction products
(4): Interpretation of results [1]
The first step of the PCR is the Sampling and Sample preparation. The sample use for the analysis is the representative of the whole lot of crops or products. Thus it is critical to ensure that the sample is not contaminated especially during the transportation [2]. Moreover, the sample size, particle size and the distribution of the raw materials also need to take into consideration as these factors will determine the number of modified gene being detected and the accuracy of the test [1] [2]. The economic of the sampling test are also one of the factors to be concern about.
All samples must be homogenized before conducting the test. Those crops sample such as soya bean, maize for to be incubated in sterile water for up to 20 hours and be blended for homogenization. Dry samples such as soya flakes or flour are to be incubated in sterile water and be homogenized, whereas, liquid samples must be well shaken before use [2].
The second step is the DNA purification. The purification process is to remove any PCR inhibitors that will affect the amplification of DNA in order to achieve a more reliable and accurate results. Examples of the PCR inhibitors are lipids, polysaccharides and polyphenols. There are 3 types of isolation procedures: the cetyl-trimethylammonium Bromide[1] (CTAB) (other references uses hexadecyltri-methylammoniumbromide[2]), DNA-binding silica columns and the combination of these 2 methods. Besides ensuring the purify of the DNA, the quality of the DNA is also important for the PCR process. The quality of the DNA is determined by the length of the DNA and the degree of degradation due to certain processing treatment.
The main step in the GMOs detection is the PCR amplification. PCR amplification enables a specific DNA target sequence to be amplified or multiple a billion times. It requires the help of the Primers, Taq polymerase and some heat treatment [1]. After the amplification, PCR-based GMO detections methods are then carried out. The methods can be classified into qualitative method or quantitative methods. Qualitative PCR amplification methods are used to determine whether any modified material are presence whereas the quantitative methods are used to find out the number (quantity) of modified material present in the foods. Quantitative methods are the commonly used methods as it is more precise and that it can specifically identify modified materials present. For instance, Event-Specific GMO detection methods belong to the quantitative methods [1]. Lastly, the interpretations of the results obtained from the above steps are carried out.
For the protein-based GMOs test, immunological methods are used. Examples of the methods are the enzyme-linked immunosorbent assay (ELISA) and the lateral flow test formats [1]. In terms of analysis time and the amount of sample needed, protein-based GMOs test are more quicker and the amount of sample needed are minimal with compare to the DNA-based GMOs test [1]. However, when in terms of the reliability and sensitively, DNA-based GMOs tests are more precise and accurate [2].
References:
1. Farid E. Ahmed. 2004. Testing of Genetically Modified Organisms in Food. 2004. The Haworth Press; United States of America. Accessed on 15 June 2008.
2. Knut J.Heller. 2003. Genetically Engineered Food; Methods and Detection. Wiley-Vch; Germany. Accessed on 15 June 2008.
(2): DNA purification/ Isolation of DNA
(3): PCR amplification and detection of reaction products
(4): Interpretation of results [1]
The first step of the PCR is the Sampling and Sample preparation. The sample use for the analysis is the representative of the whole lot of crops or products. Thus it is critical to ensure that the sample is not contaminated especially during the transportation [2]. Moreover, the sample size, particle size and the distribution of the raw materials also need to take into consideration as these factors will determine the number of modified gene being detected and the accuracy of the test [1] [2]. The economic of the sampling test are also one of the factors to be concern about.
All samples must be homogenized before conducting the test. Those crops sample such as soya bean, maize for to be incubated in sterile water for up to 20 hours and be blended for homogenization. Dry samples such as soya flakes or flour are to be incubated in sterile water and be homogenized, whereas, liquid samples must be well shaken before use [2].
The second step is the DNA purification. The purification process is to remove any PCR inhibitors that will affect the amplification of DNA in order to achieve a more reliable and accurate results. Examples of the PCR inhibitors are lipids, polysaccharides and polyphenols. There are 3 types of isolation procedures: the cetyl-trimethylammonium Bromide[1] (CTAB) (other references uses hexadecyltri-methylammoniumbromide[2]), DNA-binding silica columns and the combination of these 2 methods. Besides ensuring the purify of the DNA, the quality of the DNA is also important for the PCR process. The quality of the DNA is determined by the length of the DNA and the degree of degradation due to certain processing treatment.
The main step in the GMOs detection is the PCR amplification. PCR amplification enables a specific DNA target sequence to be amplified or multiple a billion times. It requires the help of the Primers, Taq polymerase and some heat treatment [1]. After the amplification, PCR-based GMO detections methods are then carried out. The methods can be classified into qualitative method or quantitative methods. Qualitative PCR amplification methods are used to determine whether any modified material are presence whereas the quantitative methods are used to find out the number (quantity) of modified material present in the foods. Quantitative methods are the commonly used methods as it is more precise and that it can specifically identify modified materials present. For instance, Event-Specific GMO detection methods belong to the quantitative methods [1]. Lastly, the interpretations of the results obtained from the above steps are carried out.
For the protein-based GMOs test, immunological methods are used. Examples of the methods are the enzyme-linked immunosorbent assay (ELISA) and the lateral flow test formats [1]. In terms of analysis time and the amount of sample needed, protein-based GMOs test are more quicker and the amount of sample needed are minimal with compare to the DNA-based GMOs test [1]. However, when in terms of the reliability and sensitively, DNA-based GMOs tests are more precise and accurate [2].
References:
1. Farid E. Ahmed. 2004. Testing of Genetically Modified Organisms in Food. 2004. The Haworth Press; United States of America. Accessed on 15 June 2008.
2. Knut J.Heller. 2003. Genetically Engineered Food; Methods and Detection. Wiley-Vch; Germany. Accessed on 15 June 2008.
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