Before undergraduate students take a genetics course they generally know cancer has a genetic basis and involves the proliferation of cells; however, many are uncertain about why only a subset of people have a predisposition to cancer and how that predisposition is inherited from one generation to the next.  To help students learn about these concepts, we designed a teaching unit that centers on a small-group, in-class activity.  During this activity students learn how to:

1. determine inheritance patterns for different types of cancer,
2. explain why a person with or without cancer can pass on a genetic predisposition to cancer, and
3. distinguish between proto-oncogenes and tumor suppressor genes. 

In addition to participating in the small-group activity, students watch short video clips from a documentary about breast cancer, answer clicker questions, and engage in a whole-class discussion.  A combination of pre/posttest results, clicker question answers, and performance on subsequent exam questions suggests that this unit helps students learn about the hereditary basis of cancer.