By Jonathon Carlisle
On Thursday, June 8, we filed into the lab between breakfast and lunch hours as usual, only this time we brought breakfast food samples. The purpose was to test them for genetic engineering. Everyone brought something different, with the result that it was a varied lot. The variety might ensure that some GMO samples would be present, but by accident it also ensured that everyone would be hungry again before lunchtime, irrespective of individual taste. We had rice crispies, apple jacks, and lucky charms, and thats just for cereals. There were also chocolate poptarts and cookies.
Figure 1. some name-brand food items being tested for genetic engineering
All of these delicious food items were broken down and weighed into one gram pieces before being pulverized with a pestle in five mL of water. After this, they were pulverized some more, and introduced to another five ml of water.
Picture 2. Pulverized Poptart in 10mL water
Once they were finally ground smooth enough for pipetting, we transferred 50 ul each into two separate tubes. One tube was prepared with a plant primer and the other with a GMO primer. The primers “seek-out” a specific region of DNA and amplify it, allowing us to detect the presence of plant DNA in food in one tube and genetically modified DNA in food in the other tube. We kept the tubes in ice-baths to prevent any unwanted or premature reactions. For comparison, we each prepared a known GMO sample, and a known non-GMO sample in different tubes alongside those we prepared from the food brought to lab. We centrifuged them all for five minutes, then put them in the PCR machine.
Picture 3. tubes chilling in an ice bath.
Figure 4: a blurry picture of tubes being loaded into the PCR machine.
The PCR machine will heat and cool the tubes in a way that facilitates DNA replication at the sites targeted by the plant or GMO primers present. With just a few cycles, if GMO DNA is in any of the food samples, we will be able to know it.
DAY 2: I made sure to eat breakfast before we returned next week (Tuesday June 13). We transferred the samples by pipette into an electrophoresis apparatus. When a charge is applied to the machine, the negatively charged DNA runs through the gel towards the positive end. The smaller DNA fragments run further than larger fragments given the same amount of time. By this mechanism the DNA strands are separated based on their size. By already knowing the length of DNA our plant or GMO primers amplify, we can detect their presence by a dark band in the gel at a spot characteristic of certain fragment sizes for a specific amount of run time. The intensity of a band at any spot is correlated with DNA density, and the location of the spot indicates the size of the fragments there.
Figure 5. a small sample is dropped into the electrophoresis gel.
Figure 6. Power source.
Figure 7. Result from gel electrophoresis.
We brought additional food samples this week to test for GMOs. These we tested with simpler field kits, a much faster alternative to the lab technique.
Figure 8. Food samples.
To test these, we placed a small fragment into the mesh provided inside each kit, then mashed it up well and added a test strip. The test strip is dipped in a small sample so that some of the solution slowly creeps upward by capillary action, much like a paper towel dipped in water.
Figure 9. Ground up sample ready to be tested]
The test strip will show one bar in the presence of a food sample, which means it’s working. If it shows two bars, a GMO is indicated to be present.
Figure 10. one bar, no GMO detected
Figure 11: two bars: GMO detected]
Incredibly, the only sample showing two bars was provided by our known GMO control: Jiffy corn muffins.
Figure 12. Corn muffin mix that is genetically modified.