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By Nathan Cutler
On Thursday, June 11, and Monday, June 15, John Kerrigan's biology class at Harwood Union had a special visitor from the University of Vermont. Scott Tighe is a molecular biologist from Vermont Cancer Center and has a special mission to promote genetics education in Vermont through the outreach program of the Vermont Genetics Network (VGN).
This visit was significant because Scott is a former student of Kerrigan's microbiology class (class of 1983). At the University of Vermont Tighe performs genetic analysis on diseases such as neuroblastoma, breast cancer and melanoma, to name a few.
Tighe came to the class and conducted a two-day hands-on experiment designed to teach students how to work with DNA by testing food for the presence of genetically modified genes commonly used in soy and corn products.
Using food samples brought to class by students, students conducted the following experiment. Food samples were placed in test tubes containing one milliliter of water, a ceramic ball and an abrasive. The test tube was sent through a shaking device to grind up the food sample and liberate the DNA within the food.
After allowing the food sample to settle, a small aliquot was transferred to another test tube. This liquid contained the DNA from the food sample. This mixture was then heated and centrifuged, and an additional component called Chelex was added to remove positive ions from the solution which might otherwise interfere with the next reaction.
Once the purified DNA was isolated, students then "amplified" a specific gene that is found in most genetically modified food using a technique called Polymerase Chain Reaction (PCR). PCR is very useful for amplifying a specific target DNA and finding "the needle in the haystack." It is a common technique used for medical and environmental research as well as DNA forensics.
Students used PCR to amplify a promoter gene associated with genetically modified food called CMV35s, which is actually a small piece of the entire gene used in genetically modified food. This "fragment" is actually called a promoter. In order for the gene to be implanted into the host's DNA, a promoter has to be used. A promoter instructs the host organism to replicate the inserted gene. It is like light switch. If one turns on the switch, the lights come on or, in genetics, if one has a promoter DNA, a gene gets turned on and will make the protein of interest. These promoters are great tools for genetic engineers.
The actual gene that is inserted and does the work in the plant is a natural DNA taken from the soil bacterium <MI>Bacillus thuringienesis<D> (Bt) and transplanted into corn or soy. This gene causes the plant to produce a naturally occurring protein called delta-endotoxin which is a deterrent to many insects including the nasty corn borers, a common insect pest that attacks corn plants and destroys crops.
After the DNA was amplified, it was run through an agarose gel, which is essentially a molecular sieve for DNA. This works by applying an electric current to the gel so when the DNA is present it can be separated based on size. A positive result is obtained and the correct size of CMV35s is observed on the gel. Students then photographed the DNA in the agarose gel using a UV trans-illuminator, which makes the DNA fluoresce red. The DNA was compared to a control sample and calibration standard to determine the size of what was amplified in the food samples.
After the photograph of the genes was taken, the class examined it to determine which of their foods contained GMOs. The food samples tested were Italian wafer cookies, Kashi bar, Silk milk, Captain Crunch, Peanut Butter Chocolate Corn Pops, Nature Valley chocolate chip granola bar, rice cake and Total cereal. During this experiment, students found several samples that were positive.
In this experiment, they learned that although the term "genetically modified" might sound scary, it really is not when it is understood. Genetically modifying crops or farm animals is a much debated issue. Some feel that it is good because it decreases the need for pesticides and can increase the quantity of harvest of certain crops. Others feel that genetically changing the food may have detrimental effects on health. Genetically modified crops are expensive to engineer. It takes 6 to 15 years of scientific development and millions of dollars to change the genes in just one plant. In the end, is this much time and money worth the result? Even after 15 years, the debate continues.