Biotechnology Laboratory Technician Program
Tempest in a Taco Shell?Adapted from D. Brandner
American Biology Teacher 64:433 (2002)
Detection of Genetically Modified Foods
Detection of Genetically Modified Foods
Detection of Genetically Modified Foods
• Benefits• Risks• Polymerase Chain Reaction• Lab Activity
Benefits of GM Food - Agricultural
• Improvements in productivity & profitability• For example:
Herbicide Tolerance
• Glyphosate Tolerance (Roundup Ready™)
Weed-infested soybean plot (left) and Roundup Ready® soybeans after Roundup treatment. Source:
Monsanto
• Bt Genes
Corn hybrid with a Bt gene (left) and a hybrid susceptibleto European corn borer (right). Source: Monsanto
Insect Resistance ß
Benefits of GM Food -Environmental
• Reduced use of pesticides, herbicides & fuel
• Increase Vitamin Content - Golden Rice
Benefits of GM Food - Improve Food Quality
• Delay Ripening• Allows more time for
shipping• Less loss of product
Benefits of GM Food - Improve Food Quality
• Edible Vaccines• Grown locally• Don’t require syringes
What would you rather do, get a shot or eat a potato?
Benefits of GM Food - Disease Prevention
Risks of GM Food
• Allergens
Risks of GM Food
• Pollen Drift
Risks of GM Food
Photo from the Fish and Wildlife Service (www.fws.gov)
• Harm to Environment
Detection of GM Food
• ELISA Method This example, using a test for Bt Cry1Ac, shows one
kind of test available for Bt protein. The top result is for conventional corn. There is only one pink line across the stick. The bottom result is for Bt corn. There are two pink lines across the stick, indicating that Bt Cry1Ac protein is present in the corn sample that was tested
• PCR MethodQuickTime™ and a
Photo - JPEG decompressorare needed to see this picture.
Lab Activity -Test Everyday Foods for Genetic Modifications
• Isolation of DNA• PCR• Gel Electrophoresis & Visualization
Isolation of DNA
• We performed this step for you• DNA has been isolated from a variety of
corn and/or soybean containing foods
Polymerase Chain Reaction - PCR
• A way to amplify SPECIFIC small amounts of DNA - like the small amount we isolated from the food samples
• We are targeting a region of DNA that would ONLY be present if genetic modifications have taken place
PCR
• The genetic modification is detected by using “PRIMERS” which are small pieces of DNA designed to recognize these specific segments of DNA
• The process utilizes a THERMOSTABLE DNA POLYMERASE
Thermocycler from MJ Research
PCR
• You will set up these reactions today• Wear gloves; avoid introduction of
nucleases
PCR
• To your tubes add: PCR bead (contains enzyme, buffer, salts and
dNTPs) 5ul DNA 2ul primers 18ul water
• Final volume = 25ul• Place one drop of mineral oil on top
PCR
• Tubes will be placed in the thermocycler to be amplified
• Only the region of the genetic modification will be copied over and over - millions of times
Gel Visualization and Interpretation
• Positive samples will show a band at 195bp
• Which samples do you guess will be positive?
QuickTime™ and aPhoto - JPEG decompressor
are needed to see this picture.