<prompt> Alzeihmers disease is associated withChr 21Chr 19Chr.21Chr.22  <response>: Patients with trisomy 21 have 3 copies of the gene for amyloid precursor protein and develop neurological characteristics of Alzheimers disease by midlife. Alzheimers Disease in People with Down Syndrome. Many, but not all, people with Down syndrome develop Alzheimers disease when they get older. People with Down syndrome are born with an extra copy of chromosome 21, which carries the APP gene. This gene produces a specific protein called amyloid precursor protein APP .which leads to development of Alzheimers Ref Harrison20th edition pg 2756 