Ohio Assessment for Educators (OAE) Integrated Science (024) Practice Exam

What type of genetic condition is Huntington's disease?

1. Autosomal recessive disease

2. X-linked dominant disease

3. Autosomal dominant disease

4. Mitochondrial disorder

The correct answer is: Autosomal dominant disease

Huntington's disease is classified as an autosomal dominant disease, meaning that it is caused by a mutation in a gene on one of the non-sex chromosomes (autosomes) and that only one copy of the mutated gene is necessary for an individual to express the disease. This characteristic of autosomal dominant inheritance leads to a 50% chance of passing the condition to offspring if one parent is affected. In contrast, autosomal recessive disorders require two copies of the mutated gene for an individual to exhibit symptoms, which is not the case for Huntington's disease. X-linked dominant diseases are linked to genes located on the X chromosome, and both males and females can be affected, but this does not apply to Huntington's. Mitochondrial disorders are caused by mutations in mitochondrial DNA and are inherited maternally, neither of which describe Huntington's disease. Understanding that Huntington's disease is the result of a single mutated gene from either parent helps clarify why it follows the autosomal dominant inheritance pattern, leading to its manifestation in affected individuals.