Over the past few weeks, grade 11 Biology students have had the unique opportunity to isolate, purify, amplify, and sequence DNA in their course using many techniques that are generally only found in university and forensic laboratories.
Using modern molecular biology techniques, students first extracted DNA from commercially available fish products purchased at a grocery store. Next, they conducted a PCR (Polymerase chain reaction) lab to amplify the DNA similar to how forensic scientists replicate trace DNA samples from crime scenes.
Lastly, the boys used gel electrophoresis to separate and purify these DNA samples. All the produced DNA was sent to a genetic sequencing facility the Hospital for Sick Children in Toronto with the hopes that the students could compare specific genetic markers in their samples to known DNA sequences from fish.
Interestingly, the DNA sequences revealed that the samples collected from imitation crab were not from crab at all. In fact, the meat was that of Gadus chalcogrammus, or Alaskan Pollock. In a separate sample taken from processed fish products, students discovered that the packaged fish was Oreochromis niloticus, which is commonly referred to as Nile Tilapia. This was not surprising considering that this type of fish of is one of Canada’s largest commercially farmed seafood.
Following the genetic screen, one of the samples contained a DNA sequence for Demodex folliculorum, a common, non-detrimental parasite that resides on human skin, which must have fallen into the sample when it was being prepared by one of the students. This result in itself demonstrated not only how sensitive PCR really is, but also how easily lab samples can be contaminated.
Beyond exposing students to numerous molecular biology techniques, this opportunity gave them a chance to determine the source of common seafood products, and confirm the information that is present on the packaging of these foods. Furthermore, these experiments also paved the way for additional genetic experiments that will test whether organic foods are not genetically modified (as claimed). They also introduce concepts that will be used in grade 12 DNA fingerprinting labs that identify individuals based on genes inherited from their parents.