The Great Petunia Carnage of 2017: A Clicker Case Study Using Petunias to Describe the Effect of Genetic Modification on the Biochemistry of Flower Color and Phenotype in Plants

In this single class period case study, students examine the difference between genotype and phenotype by studying the mechanisms by which commercially available petunias have been bred to have different phenotypes (flower colors). Students review the central dogma of molecular biology, connecting the phenotypes of the petunia plants to their genotypes, and the existence of a transgene in plants with unusual (orange) flowers. The case study describes the molecular and biochemical mechanisms by which the secondary metabolites that determine flower color are produced. This case is designed as a “clicker case” utilizing personal response systems or “clickers” to engage students in a large classroom setting. This approach allows for students to collaborate actively, while the instructor is leading and pacing the lecture in a way that allows engagement with large groups. As students work through the case, they work out the processes needed to add transgenes to a plant, as well as how we can detect these modifications decades later. Lastly, instructors can lead a discussion of the scientific and social issues surrounding the creation, use, and regulation of genetically modified organisms. Primary Image: Orange petunias in Helsinki railway station in 2016. Photo credit: Hany Bashandy and Teemu H. Teeri, CC BY 4.0, via Wikimedia Commons