Where Does Elsie's Hair Color Come From? A "De-Simplified" Pedigree Lesson

Abstract

Pedigree analysis is part of most Genetics curricula, but the examples traditionally used in genetics courses present phenotypes as if they were entirely and inexorably defined by genotype. This does not reflect the current state of understanding in genetics, and can inadvertently reinforce the inaccurate belief that characteristics associated with any socially-defined group is governed by genes. In order for Genetics resources to better reflect present-day knowledge, instructors need teaching resources that acknowledge the multifactorial nature of phenotypic variation. Such resources are still scarce, particularly for pedigrees. This pedigree lesson, set up as a case study, allows students to "discover" the complexities of genotype-phenotype relationships using data from a published study. Students first become familiar with the specific single nucleotide polymorphism (SNP) in a single gene associated with the phenotype of interest (hair color), then contend with a series of increasingly challenging pedigrees, the last one seeming unsolvable. They then examine a figure from the research paper, showing the broad and overlapping ranges in hair color in each of the three relevant genotypic groups. This becomes the starting point for explaining the apparent inconsistencies in the most challenging pedigree, and for discussing the real-life complexities behind phenotypes and pedigree analysis. The lesson was well received by students, and their post-lesson assignments demonstrated a nuanced understanding of phenotype. Answers to exam assessment questions showed excellent pedigree analysis skills and a keen eye for the influence of environment on phenotypes.