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.