Many students struggle with how the function of a protein can be dictated by that protein’s molecular makeup. In this case study, students learn about the structure and function of dystrophin, a protein that is involved in the contraction and protection of muscle fibers. Students read a story about a six-year-old boy who suffers from X-linked dilated cardiomyopathy due to a missense mutation in the dystrophin gene that changes the 18th amino acid from a lysine to an asparagine. Rather than cause the resulting protein to lose its function, this mutation merely weakens the overall stability of the protein because of the difference in bond strength between the R groups. As students work through the case, they answer questions and analyze data figures of thermal and denaturant melts for the wildtype and the variant protein. This case study is best suited for intermediate-level biology courses like biochemistry, cell biology, or molecular biology.