This article describes how the teaching of variation and genetics can give rise to the mistaken idea that genes are the sole determinants of our characteristics, that genes work in isolation to produce genetic disorders, such as cystic fibrosis. It goes on to discuss examples of gene environment interactions that give a more relevant and realistic account of how genes and environment interact in human genetic disease and stem cell technology. Finally, a conceptual model is introduced that might be useful for teaching, in which genes and environment are given equal status in explaining development.