The purpose of this research was to explore the way pupils of different age groups use a model to understand abstract concepts in genetics. Pupils from early childhood to late adolescence were taught about genes and DNA using an analogical model (the wool model) during their regular biology classes. Changing conceptual understandings of the concepts of gene and DNA as a result of the teaching that incorporated the model were investigated. The research design was a multiple case study enacted in four classes (Year 2, Year 5, Year 9 and Year 12). In each class, the teacher used the same wool model to engage pupils in learning about genes and DNA. The results suggest that the role of the wool model was largely determined by the pupils' prior knowledge. The model was malleable and had multiple roles in the teaching and learning process that reflected the pupils' developing conceptual understandings about genes and DNA. (Contains 1 figure and 2 tables.)