Changes in grade 10 students' (n=79) conceptions of genes during genetics instruction was studied from multiple perspectives. Ontologically, most students moved from passive to active models of genes. Affectively, students were interested in genetics but unmotivated by microscopic mechanistic explanations; however, teaching approaches were simplistic. Epistemologically, most students held intelligible or plausible--but not fruitful--conceptions. Contains 43 references. (Author/WRM)