Cross-Sectional Study of Students' Molecular Explanations of Inheritance Patterns

Genetics is a core topic in the biology curriculum of many countries. Learning genetics is difficult for multiple reasons, including the need to reason about complex mechanisms--and to link mechanisms--that occur at different time and space scales. Previous research in genetics education explores students' understandings of inheritance patterns or their understandings of molecular genetics; only a handful of studies examined how students understand the connection between molecular mechanisms and inheritance patterns. Moreover, we know little about how such understandings develop over the secondary and undergraduate levels. To address this gap, we conducted a cross-sectional interview study with middle school, high school, undergraduate, and graduate students after they had experienced "status-quo" instruction in genetics. We analyzed student responses using a cognitive model of molecular genetics that describes two key domain-specific knowledge resources: heuristics and explanatory schemas. Our findings extended this model to account for reasoning about inheritance patterns as well as identifying the knowledge resources used by students with different levels of education. This allowed us to present a snapshot of a progression describing the gradual use of these heuristics and schemas across different grades. We discuss the implications of the tentative progression for instruction aimed at supporting reasoning across time and space scales in genetics.