Building the lac Operon: A Guided-Inquiry Activity Using 3D-Printed Models

Abstract

Undergraduate biology courses rely heavily on visual representation of information. Students view images of plants, animals, and microbes, interpret data presented in graphs, and use drawings to understand how cells and molecules interact in three dimensions. Traditional teaching approaches exclude students with visual impairments and disadvantage students with disabilities that affect their interpretation and processing of visual and spatial information, and also students who simply do not identify as "visual learners." By using new technologies to develop tactile teaching tools (TTTs) that can be employed in classrooms, we aim to create inclusive learning environments and more effectively instruct diverse learners. The advent of affordable and accessible 3D printing technology makes it possible to create tactile models that represent molecules, cells, and entire organisms more accurately than traditional visual representations. We describe the assessment of a 3D gene expression puzzle as a guided inquiry learning activity in which students must correctly assemble a series of components in order to achieve an output. Upon completion of the puzzle, the TTT provides tactile feedback through vibration to signal transcriptional activation. Analysis of pre- and postassessment performance demonstrated statistically significant increases in individual students' paired assessment scores in two different classroom implementations, with a greater effect size at a rural minority-serving institution than an urban R1 university. These encouraging preliminary data suggest that TTTs with guided-inquiry learning disproportionately benefit disadvantaged student populations and could serve as a tool in leveling the playing field when teaching abstract biological concepts in diverse educational settings.

FIGURE 1

3D-printed lac operon tactile teaching tool set. A) The yellow LacI repressor protein is shown binding to the operator site within the promoter. B) The allolactose (magnetic marble) is shown binding the LacI repressor, pulling it off of the operator sequence. With LacI unbound, the red/white RNA polymerase is able to bind to specific −10/−35 regions in the lac promoter as shown in C. C) Magnets are used to simulate interactions between components. The model utilizes a simple circuit with the battery contained within the RNA polymerase and a vibration motor contained in the gray DNA box. When the RNA polymerase binds to specific −10/−35 regions in the lac promoter, the circuit is completed, and the model begins to vibrate, representing transcriptional initiation.

FIGURE 2

Impact of lac operon GIL activity on student learning, demonstrated by performance on pre- and post-assessments. A) Pre- and post-assessment scores are shown as violin plots. The width of the plot represents the percentage of students receiving a given score. Dotted lines represent quartiles, and solid red lines represent medians. Individual students’ linked pre- and post-assessment scores were measured using a Wilcoxon matched pairs signed-rank test (****, p < 0.0001). B) The percentage of students answering each assessment question correctly is shown for NCSU (left) and UNCP (right). Open bars represent the pre-assessment, and filled bars represent the post-assessment.