Genetics is often a fascinating but difficult subject for middle level students. They can see the results of genes in every organism, but trying to visualize what happens at the level of genes is challenging for concrete thinkers. The author discusses an approach that helps students understand how genotypes can translate into phenotypes, then presents an activity that helps students understand how genotypes can translate into phenotypes. In this lesson, students examine gummi bears and see whether they can determine the genotype for color in three generations of a bear family. Using gummi bears and gummi dolphins gives students an opportunity to solve problems using Mendel's model and then to revise the model when the data do not fit. Being able to use a model to solve novel problems and then to develop a new model to explain anomalous data helps students to understand each model better and experience the way real scientists do inquiry. (Contains 2 figures.)