Beyond Punnett squares: Gains and challenges for learning quantitative genetics in an inquiry-based introductory biology lab course

Background/Question/Methods

Introductory biology typically stops short of teaching quantitative genetics, confining instruction to transmission of single-gene Mendelian traits. Given the driving question “What determines phenotype (P=G+E)?”, we developed a 4-week unit for our large inquiry-based laboratory course focused on the inheritance and expression of a multi-genic trait in varying environments. We utilized Brassica rapa Fast Plants ® as a model organism to study the phenotype of anthocyanin pigment intensity.  By the end of this unit, students should have been able to: 1.) develop and carry out an experiment to provide evidence about how artificial selection and environment influence phenotype, and 2.) use data as evidence to explain inheritance and expression of quantitative traits.

The 4-week lab unit was designed so that week 1 served as an introduction to the B. rapa system, parental and F1 seed stocks, the anthocyanin pigment color index, and artificial selection for purple plants. In week 2, 4-member research teams gave a “feedback presentation” to gather input on their experimental design and hypotheses predicting the relative pigmentation intensity of F1, F2-selected and F2 non-selected (drift) populations exposed to control and experimental environmental conditions of their choice. In week 3, students gathered preliminary data on the pigment intensity of newly germinated seedlings, practiced data analysis, and began to draft a scientific poster.  In week 4, students gathered their final data and completed their individual posters.

Results/Conclusions

In order to evaluate achievement of learning goals, we scored student posters using a coding rubric developed to measure students’ use of data and language in their explanations of inheritance and expression of anthocyanin pigment intensity. In addition, students filled out a pre- and post-unit survey that assessed their exposure to and knowledge of quantitative genetics, and their confidence in achievement of the learning goals.

Given preliminary review of 78 student posters, we found moderate to sophisticated explanations for how environment influenced expression of pigment intensity. Conversely, students had limited capacity to use data in their explanation of the genetics behind artificial selection and increase in allele frequency involved in expression of pigment intensity. Surveys revealed improved understanding of relevant terminology, an increased familiarity with a diversity of genetics concepts, and an intriguing increase in students’ association of genetics to evolutionary biology. We will present additional analysis for student learning gains and challenges, and will provide suggestions for next steps for teaching and learning of quantitative genetics in an introductory biology course.