Huntington’s disease (HD) is a devastating neurodegenerative disorder that affects movement, cognition, and behavior. My latest case study provides an engaging and educational resource for biology teachers to help students explore the genetic and physiological aspects of HD.
This case study follows Eleanor Thompson, a grandmother whose family begins noticing subtle changes in her behavior and motor skills. As her symptoms progress, she visits a neurologist, where she is diagnosed with Huntington’s disease. The case study explains the underlying genetic cause—an expanded CAG repeat in the HTT gene. Learn how the degeneration of the basal ganglia leads to uncontrolled movements, known as chorea. It also explores the autosomal dominant inheritance pattern, highlighting the risks to her children and grandchildren.
Use this case study to:
✅ Explain the molecular basis of genetic disorders
✅ Discuss the role of the basal ganglia in motor control
✅ Explore ethical considerations in genetic testing
✅ Encourage critical thinking about treatment and patient care
I include this case with the unit on DNA Structure, which also explores how mutations in chromosomes can lead to changes in gene expression. In particular, I focus on trinucleotide repeats as they relate to amylase production (AMY1) in humans. Then we transition to how repeated sections of DNA can also cause problems, as in the case of Huntington’s disease.
I also include two graphs related to Huntington’s disease. Students can still struggle with graph analysis, and this unit occurs near the time of state testing. It’s a good refresher on how to analyze data!
Case Study Highlights:
🔬 Introduction: Recognizing the Symptoms – Students learn how Huntington’s disease begins with cognitive and motor changes, including forgetfulness, irritability, and involuntary movements.
🏥 Diagnosis: A Visit to the Neurologist – The neurologist performs cognitive and movement tests before confirming HD with genetic testing. The case study explains how the degeneration of the basal ganglia leads to involuntary movements, known as chorea.
🧬 Understanding the Genetic Cause: The Role of CAG Repeats – This section delves into molecular genetics, explaining how an expanded CAG repeat in the HTT gene leads to a malfunctioning huntingtin protein, causing neuronal damage.
👨👩👧 Inheritance Pattern: Risks to the Family – Students explore the autosomal dominant inheritance pattern, understanding the 50% risk that Eleanor’s children have of inheriting the disorder and the ethical dilemmas of genetic testing.
💊 Treatment and Patient Outcomes – While there is no cure, the case study examines medications for symptom management, physical therapy, and the role of genetic counseling in helping affected families plan for the future.
