Is Tori seeing red? A lesson for first-year biology that unveils the complexity of phenotypic variation with pedigree analysis

Introductory biology instructors contend with the tension between the inherent complexity of the discipline and cognitively overloading their students. While oversimplification may promote misconceptions, without sufficient simplification, students may fail to grasp a basic understanding of disciplinary concepts. In genetics education, evidence is mounting that the risks associated with oversimplifying far outweigh the benefits, as emphasizing Mendelian principles while neglecting the role of environment not only fails to reflect our current understanding of genes and genomes but can also inadvertently reinforce the misinformed belief that genes alone determine people's physical, cognitive, and behavioral characteristics. Examples and activities featuring human pedigrees can be particularly insidious. While excellent tools for helping students apply fundamental genetics concepts and practice analytical skills, they reduce phenotypic variation to a dichotomous "affected" vs. "unaffected" model with perfectly Mendelian inheritance and the underlying, unspoken assumption that phenotype is entirely determined by genotype. There is a need for instructional resources that present genetics in a way that better reflects present-day knowledge, make light of the complexities hidden behind pedigree charts, and allow students to appreciate the multifactorial nature of phenotypic variation, and the challenges of classifying individuals into discrete categories. To help fill this gap, we offer an engaging lesson that promotes critical pedigree analysis skills and honors the complexities of phenotypic variation.