Linking Genotype to Phenotype: The Effect of a Mutation in Gibberellic Acid Production on Plant Germination

Abstract

Basic concepts in genetics and plant development are often taught in lecture courses without a lab component. This approach provides students with the content knowledge, but fails to make connections to research opportunities and real-world applications of the science. To help address this deficiency, we developed a hands-on activity demonstrating the effect of the plant hormone gibberellic acid (GA) on germination, and tested it within the undergraduate course lecture setting. The activity takes advantage of a mutation in a GA biosynthesis gene, demonstrating the requirement of this important hormone for normal plant development. In this exercise, students investigate the effects of a GA supplement on the germination rate of GA-producing wild-type seeds versus GA-deficient mutant seeds. Based on their observations, students are able to identify the genotype of an unknown seed sample. The simple design allows students to learn about the importance of using controls, the difference between wild type and mutant, and the phases of plant germination including the role of GA. The teachers can also use student responses to the assignments to determine and clarify common misconceptions students have developed as a result of insufficient prior knowledge. By helping students make connections between different concepts within the covered material, this lesson enables teachers to accomplish higher level learning goals, thus complementing and adding value to the lectures.