This case study reviews the central dogma of molecular biology and the mannose-6-phosphate (M6P) pathway.  Four biology students are tasked with identifying a genetic disorder, specifically I-cell disease (mucolipidosis type II) and its pathophysiology for a group presentation.  Over the course of their ensuing conversation, they review patterns of inheritance, the process of protein synthesis, protein translocation, and bone remodeling; they also make connections to histological, radiographical, and hematological results. To complete the case, students are expected to have a basic knowledge of cellular organelles and their functions and protein synthesis. The case consists of five sections, one of which, Part IV, has two versions. “Part IV – Conclusion” makes the case suitable for lower-level undergraduate students taking courses in general biology, genetics, human anatomy and physiology, or human health and disease. The alternative “Part IV – Conclusion (Extended Version)” makes the case suitable for upper-level undergraduate students in cell or molecular biology courses.