The Huntington disease gene HTT (The Huntington's Disease Collaborative Research Group, 1993) was cloned in 1993, 10 years after the linkage of the gene to chromosome 4 in 1983 because this gene was located near the chromosome 4p terminus, which was composed of many repetitive elements where a considerable number of recombination events in meiosis occur. The gene discussed is HTT; the disease is Huntington disease.