The central dogma of biology is a foundational concept that provides a scaffold to understand how genetic information flows in biological systems. Despite its importance, undergraduate students often poorly understand central dogma processes (DNA replication, transcription, and translation), how information is encoded and used in each of these processes, and the relationships between them. To help students overcome these conceptual difficulties, we designed a clicker-based activity focused on two brothers who have multiple nucleotide differences in their dystrophin gene sequence, resulting in one who has Duchenne muscular dystrophy (DMD) and one who does not. This activity asks students to predict the effects of various types of mutations on DNA replication, transcription, and translation. To determine the effectiveness of this activity, we taught it in ten large-enrollment courses at five different institutions and assessed its effect by evaluating student responses to pre/post short answer questions, clicker questions, and multiple-choice exam questions. Students showed learning gains from the pre to the post on the short answer questions and performed highly on end-of-unit exam questions targeting similar concepts. This activity can be presented at various points during the semester (e.g., when discussing the central dogma, mutations, or disease) and has been used successfully in a variety of courses ranging from non-majors introductory biology to advanced upper level biology.