For example, the existence of amyloid in neuritic plaques in AD, the genetics of inherited AD, the contribution of mutations of amyloid precursor protein (APP), Alzheimer-like changes that are found in middle-aged patients with Down syndrome, the molecular biology of Aβ production from APP, the neurotoxicity of amyloid in tissue culture, and detection on transgenic mouse models of AD with human mutant genes, are all indicators of the amyloid hypothesis of AD. The gene discussed is APP; the disease is Alzheimer disease.