Discussion Questions

1. Review your understanding of gene mutations. Define a gene mutation and explain why some mutations are neutral while others cause a change to the protein synthesised by the gene.

2. Mutations whose effects take hold after child-bearing age have quite different patterns of allele survival to mutations whose effects appear earlier in life. Use information about the age of onset of Huntington’s disease to discuss this statement.

3. Most people with HD are heterozygotes. Homozygotes for HD are very rare. Discuss this statement.

4. Discuss the relationship between number of CAG repeats and age of onset of disease.

5. Discuss the relationship between types of symptoms Huntington’s sufferers experience and the parts of the brain affected.

6. The number of CAG repeats is an indicator of development of Huntington’s disease. At 40 and above repeats all individuals are affected. Individuals 26 and below are unaffected and their offspring is unaffected. However, if there are 27–35 repeats, the individual is unaffected, yet any offspring and future generations are possibly affected. Explain why this might be.

7. Human disorders are increasingly being diagnosed and treated using biotechnological applications such as stem cell therapy. Explain how stem cell therapy might be used to treat brain diseases like Huntington’s.

Scholarship-Level Question

8. Analyse and discuss the inheritance of Huntington’s Disease in humans. In your discussion consider the following:

• The genetic factors and processes involved in the inheritance of Huntington’s disease 
• Factors affecting the likelihood of inheriting the disease and factors affecting expression of the disease