When a 30-year-old genetic counselor learns that her 38-year-old sister has developed early onset familial Alzheimer’s disease (EOFAD), a dominantly inherited disorder that led to their father's death at age 42, she struggles with whether to undergo genetic testing and whether to have children. This interrupted case study examines the impact of genetic testing on people and their families when there is no treatment or cure for a disease. It covers principles of Mendelian inheritance as well as genetic and reproductive technologies ,such as gene tests, pre-implantation genetic diagnosis, and in vitro fertilization. It can be used in introductory biology courses for both majors and non-majors or adapted for more advanced courses in genetics and molecular biology.