无独有偶, 那我来贴一个检测转基因的方法吧, 前几天考试前整理的{:soso_e113:}
Examples of GMOs l GM tomato: has been insertedgenes from snapdragon that contains much anthocyanin l GM rice: contains much vitaminA l GM salmon: grows faster, grows bigger,contains less fat GM products: papaya, banana, maize, soy bean, potato, strawberry,sunflower, cotton, etc. How to avoid GM pollution Set up buffer zone between GMplants and non GM plants. After harvested, destroy those plants that grew inthe buffer zone.
What is gene? Particular functional regions ofnucleotide sequence of DNA are defined as genes. Each gene is composed of apromoter, an open reading frame and a terminator. Promoter works as a switcherto determine whether a gene is active or inactive. Terminator is the endpointof a gene. DNA sequences within the ORF of a gene determine the sequence ofamino acid in protein. Human genome contains at least 30,000 genes.
Methods Ti Plasmid Novel gene sequences are insertedin the Ti plasmid of the bacteria. Therefore, the Ti plasmid will pass throughplant cells and integrate into the plant chromosome. Particle gun (gene bombardment) A physical technique that punchestarget cell walls with tiny particles of tungsten/gold coated DNA.
Why are products being tested for GMO? 1. Why being test; 2. Qualitative or quantitative; 3. Raw orprocessed; 4. Homogeneous or not Materials from farm to finalproducts should be tested for GMO in order to meet the requirements of worldtrades as well as different labeling systems. During GMO testes, qualitativescreenings are used to identify different kinds of genetic transformationmethods (e.g., Ti plasmid, particle gun). Raw materials can be analyzed usingDNA or protein based detection methods. However, for processed food, DNAdetection should be a better way to analyze GMO because proteins inside mightbe denatured during processing. High processed food such as sugar and oilusually won’t be detected but will analyze their components before processing.
Protein detection methods ELISA (Enzyme Linked Immunosorbent Assay) uses antibodies to recognize specific proteins. 1. Antibodies for target proteinare bound on the wall of well plate 2. Target protein (is any) willbind to antibodies 3. Another antibody with enzymewill be added in and bind with proteins 4. Appropriate dye will react withenzyme and show in color l [pros] Both qualitative and semi-quantitative method l [pros] Relatively fast (2~4 hours) and low cost l [pros] Easy to manage l [Cons] less sensitive than DNAassay l [Cons] the development ofantibodies cost times l [Cons] ELISA kits need to bestored at 4 degree Celcius Limitation: some GMO won’t produce detectable level of proteins Lateral Flow Strips is a variation of ELISA that the antibodies are fixed on a test strip. 1. Target GM proteins will bind to antibodies coated with colloidalgold 2. The protein-antibody complexes will flow to the fixed detectionantibodies 3. If the result is positive, the detection zone will turn red l [pros] rapid act (several mins), can be used on the front line l [pros] disposable and cheap l [pros] Easy to manage without other equipments l [Cons] low sensitivity l [Cons] the development ofantibodies cost times DNA Detection Methods 1. DNA extraction: use chemical reagents(usually anionic detergents) to break down cell for releasing DNA. Then removeproteins and other cellular components and purify DNA by precipitating intoalcohol. 2. DNA amplification: use Polymerase Chain Reaction method toamplify target DNA. l Raise temperature to nearboiling that cause DNA to denature into single strands l Decrease temperature and letspecific primers bind to the single DNA strands l Raise temperature a little bitto active the enzyme (polymerase) by binding to primers and doing DNAduplication l Repeat several cycles until getenough DNA copies 3. The junction site of plantgenome and inserted gene (from promoter to terminator) can be used fordetecting GM under event-specific amplification. l [pros] very sensitive l [pros] every tissue can be used ‘cause every cell contains the sameDNA l [pros] GM portion can be relatively quantified l [Cons] time consuming and veryexpensive l [Cons] need skillful operator,need laboratory data to support
大体来说分protein detection和DNA detection, 考之前不明所以, 考完照样一知半解~{:soso_e134:}
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发表于 2014-5-21 20:53
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