An individual is diagnosed with Huntington Disease if they have a genetic mutation on their fourth chromosome
The gene located on their fourth chromosome, encodes a protein called huntingtin, which is distributed in certain regions of the brain, as well as other tissues of the body
Arrow indicates where the fourth chromosome is located
Mutated forms of the HD gene contain abnormally repeated segments of deoxyribonucleic acid (DNA) called CAG trinucleotide which results in the synthesis of huntingtin proteins that contain long stretches of molecules of the amino acid glutamine.
When these abnormal huntingtin proteins are cut into fragments during processing by cellular enzymes, molecules of glutamine come out from the ends of the protein fragments, causing the fragments to attach to other proteins
The resulting clumps of proteins have the potential to cause neuron (nerve cell) dysfunction
The formation of abnormal huntington proteins leads to the degeneration and eventual death of neurons in the area of the brain that controls movement (basal ganglia)
When these neurons are destroyed the patient will begin experiencing involuntary movements throughout their body