**hello all, things i post in blog are the summarise form :) for more detailed info please refer to the research file which i had posted in file exchange or the references given :)
Detection of Genetically Modified Food. ( DETECT DNA in GM food )
Two basic methods:
1) test for food product of a transgene which is a protein.
~ ELISA (Enzyme Linked ImmunoSorbent Assay)
~ level of protein measured
~ protein is bind to antibodies which is link to an enzymes.
~ specific protein detected when the protein reacts which the substrate.
~ react between antibodies and protein inserted
~ can be detected by colour change through quantative results.
~ not effctive on processed food such as canned food (high temperature teatment may destroy the protein. )
~ cheaper than DNA
~ save time
~ less specific than ELISA
~ less sensitive
~ gives qualitative and quantitative results.
2) test for presence of DNA from a transgene or gene cassette.
~ polymerase chain reaction (PCR) test to detect foreign DNA in genetically modified food [MORE COMMONLY USE]
[ for DNA isolation, PCR DNA Amplification and gel electrophoresis analysis, please refer to the reference listed below post from Madison Area Technical Collegue , silde 12 to silde 14 ] :))
~ results are obtained through gel electrophoresis
~ more expensive
~ more time needed
~ ineffective in detecting high heat treatment processed GM food, refine oil from GM crops, however can be over come by Real Time PCR that uses fluorescence to monitor the PCR amplification process
~ detectable at low levels
~ more specific than ELISA
~ more sensitive
~ produce qualitative answer, only get quantitive results if real tiem PCR is used
Polymerase Chain Reaction
Quantitative detection (QPCR): test for amount of GMO present
- quantitative real-time PCR (QRT-PCR) is the most effective way for GMO detection.
- To quantify the amount of amplified product, fluorescent dyes such as SYBR Green I or fluorophore containing DNA probes are being used.
- results are analyze by Gel Electrophresis of DNA. QRT-PCR
Qualitative detection: show whether GMO are present but not the amount
- Test by Q-PCR or multiplex PCRResult can be analysed by gel electrophoresis.
Methods of Genetically Modifying Food. ( INTRODUCE DNA in GM food )
~ introducing new genetic material into host
Three main methods to introduce foreign DNA:
1) Physcial Methods (particle gun and electroporation)
2) Chemical Methods (polyethyleneglycol and calcium chloride)
3) Biological Vectors (Ti-plasmid from Agrobacterium) [most commonly used] :
~ transgene ( DNA to be transferred ) introduced with second vector which is
~ the Ti plasmid of Agrobacterium tumefaciens
~ for transgene to work effectively in its new host, it had to be controlled by promoter and terminator sequence which is known as gene cassette when grouped.
~ common terminator: Ti plasmid in Agrobacterium tumefaciens
~ common promoter: CaMV35S promoter
source taken from:
- Madison Area Technical Collegue (2002). Chapter 5. PCR-Based Detection of Genetically Modified Food. Retrieved on 25 June 2008 from: http://ucbiotech.org/edu/edu_aids/5-brandner.pdf
- Asian Food information Centre. (2004). Detecting Genetically Modified Food. Easier said than done. Retrieved on 21 June 2008 from: http://www.afic.org/Detecting%20Genetically%20Modified%20Foods%20-%20Easier%20said%20than%20done.htm
Some points found on GMF in Singapore.
- GMF are not halal due to animals products are also being used to genetically modified.
- research shows that GM crops are halal. however if the gene inserted is from animals DNA., it is not certified as halal.
- In Singapore, products such as corn, canola oil, soy bean are genetically modified.
- Labeling of GM food in Singapore is not compulsory
- So far there is no legalization and guidelines for the labeling of GMF.
- GM rice are not grown commercially in Singapore.
- The price of GM seed is twice of the normal seed.
Source taken from:
- GMAC Singapore. Singapore press holdings. (2008). GM crops a viable option for food crisis? Retrieved on 15 June 2008, from http://www.gmac.gov.sg/News/2008/2008_05_12.html
- GMAC Singapore. (2007). Genetically Modified Food. Retrieved on 15 June 2008, from: http://www.gmac.gov.sg/Index_FAQs_Genetically_Modified_Foods.html#six [ also state which are the countries which approved GMF and what are the crops that are approved plus some other good info abt GM ]
