Upper school students in Meredith Moore’s psychology class recently explored a fundamental question: how do our genes and life experiences shape the way we perceive the world?
Through the PTC lab, students explored how sweet, salty, and bitter tastes are acquired. For some individuals, broccoli, Brussels sprouts, cabbage, or kale can have an extremely bitter taste, which is evidence of TAS2R38, one of more than 30 genes involved in detecting bitter flavors. But genetics only tells part of the story. Environmental factors and prior experience can also explain why individuals dislike specific tastes.
Students put their taste buds to the test in a two-part experiment. First, they tasted paper treated with PTC, a bitter chemical compound. Some students recoiled at the taste; others showed no reaction. This initial test provided students with an indication of whether they might carry the gene.
Then the class moved on to DNA analysis. Students collected cells from inside their cheeks and used a technique called restriction digestion—an enzyme-based process that cuts DNA only at specific sites. If a student carries the TAS2R38 gene, the enzyme would cut their DNA; if not, the DNA remains intact. The results show up as bands on a gel image. Two bands indicate that the enzyme has cut the DNA, suggesting that a gene is present. A single band indicates that no cut occurred and that the gene is absent.
The PTC lab introduces the abstract concept of how the environment and heredity influence genes, as students examine their own DNA and connect it to their personal experiences. The results are often surprising and lead students to further inquire into why the PTC paper does not taste bitter despite evidence that they carry the gene. Students can’t help but make connections and further question the relationship between nature and nurture, and why having a gene does not guarantee a trait.
By grounding complex scientific ideas in their own bodies and experiences, students come to see that a single factor rarely determines human traits. The PTC lab reinforces that understanding the world means sitting with complexity, asking better questions, and recognizing how biology, environment, and experience intersect. It’s a reminder that learning is most powerful when students are given the space to wonder.
