Huntington's Disease on the fourth autosomal chromosome

Huntington's Disease effects the fourth autosomal chromosome. The problem with this DNA causes a CAG repeat more time than it has too. However, with a person who has HD, it repeats 36 to 120 times. This gene is dominant and is passed down through generations. If one of the parents have Huntington's Disease their offspring has a 50% chance of getting the disease. If both parents have the disease then all the children will have it. The picture below is a pedigree showing the off spring with a parent who has the disease and a parent who doesn't.

This shows how Huntington disease is a dominant gene and is passed through generation to generation disease.