The correct answer is autosomal gene on chromosome 4.
All humans have two copies of the Huntingtin gene (HTT), which codes for the protein Huntingtin (Htt). The gene is also called HD and IT15, which stands for 'interesting transcript 15'. Part of this gene is a repeated section called a trinucleotide repeat, which varies in length between individuals and may change length between generations. If the repeat is present in a healthy gene, a dynamic mutation may increase the repeat count and result in a defective gene. When the length of this repeated section reaches a certain threshold, it produces an altered form of the protein, called mutant Huntingtin protein (mHtt). The differing functions of these proteins are the cause of pathological changes which in turn cause the disease symptoms. The Huntington's disease mutation is genetically dominant and almost fully penetrant: mutation of either of a person's HTT genes causes the disease. It is not inherited according to sex, but the length of the repeated section of the gene and hence its severity can be influenced by the sex of the affected parent.
HD is one of several trinucleotide repeat disorders which are caused by the length of a repeated section of a gene exceeding a normal range.The HTT gene is located on the short arm of chromosome 4
