Gene expression is a highly theoretical concept that requires advanced reasoning skills to comprehend. Often, students receive instruction but fail to replace prior conceptions and thus do not benefit. In order to investigate the reason for this failure, we used a directed inquiry activity that uses concrete analogies in both majors and non-majors biology courses at the community college and university levels. Results showed that the effect of this active learning approach was dependent on the student population; students with less prior exposure to the material experienced higher learning gains. Theoretical implications about the effects of prior conceptions on learning as well as instructional implications for teaching theoretical concepts are discussed. (Contains 3 figures and 3 tables.)