Probing visual literacy skills reveals unexpected student conceptions of chromosomes

Molecular biology can be difficult for undergraduate students because course content is often taught using highly-abstract visual representations. Genetic concepts can be depicted with lines, letters, shapes, and symbols, and students need to engage their visual literacy skills to appropriately decipher these abstract representations. We previously found that undergraduate course materials almost always represent chromosomes in abstract forms, such as "X" shapes or straight lines with a dot for the centromere. We hypothesized that students struggle to apply their visual literacy skills to accurately interpret these abstract representations of chromosomes, which may be related to the frequently-documented incomplete or incorrect ideas students have about chromosome structure and function. To explore students visual literacy related to representations of chromosomes, we conducted 35 semi-structured interviews with students who had taken at least a year of biology courses. We asked them to sketch chromosomes, interpret an abstract representation of chromosomes, and use the abstract representation to answer a question about meiosis. We found that 97% of participants (34 of 35) held conceptual errors related to chromosome structure and function. These conceptual errors were often not evident in participants verbal definitions of chromosomes and were only revealed in their sketches or explanations of their sketches. We found that participants frequently misinterpreted X-shaped representations of chromosomes, mistook unreplicated homologous chromosomes as separated sister chromatids, and held misconceptions related to the structure and function of centromeres. These findings have implications for how chromosomes are taught in biology courses. We recommend that instructors explicitly discuss the conventions and norms of representing chromosomes as a pathway for increasing students visual literacy in molecular biology.