In most people, a gene called huntingtin or HTT on chromosome 4, contains a triplet repeat, where the nucleotides C, A, and G are repeated 10-35 times in a row.
The huntingtin gene, also called the HTT or HD (Huntington disease) gene, is the IT15 ("interesting transcript 15") gene, which codes for a protein called the huntingtin protein. The gene and its product are under heavy investigation as part of Huntington's disease clinical research and the suggested role for huntingtin in long-term memory storage.