The Huntington’s Disease (HD) gene (HTT) is located on
chromosome 4, and the age of onset of the condition is closely
related to the repeat-expansion size within this gene. Recent
research shows that a particular variant on chromosome 15 acts as a
modifier for the condition. Someone with a repeat expansion in
their HTT gene as well as this modifier variant will develop HD
symptoms approximately six years earlier than someone without this
modifier variant. A woman with Huntington’s disease...