<Ul> <Li> 40 or more CAG repeats: full penetrance allele (FPA). A "positive test" or "positive result" generally refers to this case . A positive result is not considered a diagnosis, since it may be obtained decades before the symptoms begin . However, a negative test means that the individual does not carry the expanded copy of the gene and will not develop HD . The test will tell a person who originally had a 50 percent chance of inheriting the disease if their risk goes up to 100 percent or is eliminated . A person who tests positive for the disease will develop HD sometime within their lifetime, provided he or she lives long enough for the disease to appear . </Li> <Li> 36 to 39 repeats: incomplete or reduced penetrance allele (RPA). It may cause symptoms, usually later in the adult life . There is a maximum risk of 60% that a person with an RPA will be symptomatic at the age of 65 years, and a 70% risk of being symptomatic at the age of 75 years . </Li> <Li> 27 to 35 repeats: intermediate allele (IA), or large normal allele . It is not associated with symptomatic disease in the tested individual, but may expand upon further inheritance to give symptoms in offspring . </Li> <Li> 26 or fewer repeats: Not associated with HD . </Li> </Ul> <Li> 40 or more CAG repeats: full penetrance allele (FPA). A "positive test" or "positive result" generally refers to this case . A positive result is not considered a diagnosis, since it may be obtained decades before the symptoms begin . However, a negative test means that the individual does not carry the expanded copy of the gene and will not develop HD . The test will tell a person who originally had a 50 percent chance of inheriting the disease if their risk goes up to 100 percent or is eliminated . A person who tests positive for the disease will develop HD sometime within their lifetime, provided he or she lives long enough for the disease to appear . </Li> <Li> 36 to 39 repeats: incomplete or reduced penetrance allele (RPA). It may cause symptoms, usually later in the adult life . There is a maximum risk of 60% that a person with an RPA will be symptomatic at the age of 65 years, and a 70% risk of being symptomatic at the age of 75 years . </Li> <Li> 27 to 35 repeats: intermediate allele (IA), or large normal allele . It is not associated with symptomatic disease in the tested individual, but may expand upon further inheritance to give symptoms in offspring . </Li>

Huntington’s disease is associated with damage to which of the following structures