However, the Aβ sequence is unique in APP, and the amyloid fibrillar form of the Aβ sequence of 40–42 amino acid peptide of which is the primary component of amyloid plaques found in the brains of individuals with Alzheimer's disease and Down's syndrome, can be generated only from APP through its proteolysis. The gene discussed is APP; the disease is early-onset autosomal dominant Alzheimer disease.