This study examines students' understanding of the normative connections between key concepts of cell division, including both mitosis and meiosis, and underlying biological principles that are critical for an in-depth understanding of genetic inheritance. Using a structural equation modeling method, we examine middle school students' understanding of these relationships. A total of 209 seventh-grade students participated in this study and completed a technology-enhanced unit on genetics. Content-based assessments were administered to all students. Findings from a confirmatory factor analysis supplemented with an analysis of students' responses revealed a strong relationship between the concepts of genetic inheritance and cell division and provided evidence of the nature of the difficulties that students have when trying to understand these concepts. Specifically, students were challenged to demonstrate an integrated understanding of the differences between mitosis and meiosis processes. Also some students struggled to explain the importance of these processes as they relate to passage of genetic information. This study offers the science education field further insight into younger students' learning about genetic inheritance and informs the design of effective science learning materials at the middle school level. (Contains 10 tables and 2 figures.)