For the past 60 years, teaching and learning the science of inheritance and biological variation has largely been centered in Mendelian genetics. In classrooms, genetics instruction generally focuses on traits controlled by a single gene, with genotype the primary determinant of phenotype and little to no effect from other genes or of the environment (McElhinny et al. 2014). Traits used as phenomena generally have two to three discrete phenotypes (wrinkled or smooth, short or tall), which are inherited in a dominant/recessive pattern. Students participating in learning environments designed from the perspective of Mendelian genetics should be able to use a Punnett square to make predictions about the genotypic ratios of offspring from parental crosses and should understand how genotype determines phenotype in traits inherited in a dominant/recessive pattern. However, the reliance on this framework of inheritance does not support students to appreciate or explain the true complexity of human variation. After learning the Mendelian curriculum, many students attempt to apply deterministic Mendelian logic to the inheritance of all traits, assuming that there must be “a gene for” traits like eye color, skin color, personality, and intelligence and that they are inherited in the same dominant/recessive pattern as the Mendelian traits they studied in the classroom (Mills Shaw et al. 2008; Radick 2016).