By contrast, the BACHD mouse expresses the full-length human mutant huntingtin gene with 97 glutamine repeats under the control of endogenous htt regulatory machinery on a bacterial artificial chromosome, and has been less widely studied but also has been shown to mimic some aspects of HD pathophysiology and behavioral abnormalities 4,9,20, including circadian abnormalities 14,21. This evidence concerns the gene HTT and Huntington disease.