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Monday, September 15, 2014

Looking for Frankenfood

The students in my third year lab course are about to test various food products to see if they contain any DNA from genetically modified organisms. They'll be using a variety of PCR primers to detect the Cauliflower mosaic virus 35S promoter and the nopaline synthase terminator sequence from the Ti plasmid of Agrobacterium tumefaciens [see Roundup Ready® Transgenic Plants ].

Every student has to bring in their own food sample to test but I'll be providing a number of "controls" that I picked up in the cafeteria and at the grocery store. Which ones are Frankenfood?

We're using some additional sets of primers as controls. One set detects a chloroplast gene (rbcL). We have two sets of primers for corn-specific genes (invertase and zein) and one set for a soybean specific gene (lectin). An important part of the exercise is figuring out what controls to use and what DNA samples to analyze. Each group of two students can do 24 PCR reactions. It's going to be a challenge for them to figure out which reactions are the most important.

(They were told that corn and soy products are most likely to test positive in the GMO assay.)


  1. I ate university residence food for two years. I am convinced that it was all Frankenfood.

  2. That's funny, tomorrow I'm sending out two samples of possible Rose Rosette Virus infected plant cuttings to the University of Arkansas for similar testing to confirm the diagnosis (by none other than Ioannis Tzanetakis, an author on Laney et al 2011 - a landmark paper for the rose pathology world). I would love to do the PCR and run the gels myself but we don't have a set-up for that at work. If there's a customer demand and I can show that to management I might be able to get my hands on the materials and would have to seek some input from Tzanetakis and you, Larry!

  3. Perhaps you can post a brief report after this lab, Larry. I would be interested in the overall success of the lab exercise, which I presume would primarily rest upon the success of a DNA extraction step from the various food products. Have you conducted this exercise in other years?

    1. This is my first, and last, time running this lab. I'm filling in for the regular facutly member who's on maternity leave. We've been running a similar lab for many years. The particular DNA extraction method we use was worked out four years ago and it seems to be quite successful for most foods. There are lots of other steps where things can go wrong. :-)

  4. "Which ones are Frankenfood?"

    All of them:

  5. An interesting control might be a soil sample which may contain Agrobacterium. This would test positive for the NOS terminator, if there are nopaline-type Agro strains in that sample, but negative for 35S.