Several genetic factors have been identified that play a role with genes that are associated with Alzheimer's Disease (AD).

Amyloid precursor protein on chromosome 21. This is a genetic factor also associated with Down's syndrome; and explains the association between Down's syndrome and Alzheimer's Disease.

Presenilin genes on chromosomes 14 and 1. Although rare, these are associated with AD symptoms occurring before the age of 50.

Apolipoprotein E (ApoE) gene on chromosome 19. This is most interesting because it is both negative and positive. The e4-type is linked to significantly higher risk for AD, the e2-type is linked to significant protection from AD symptoms.

Although it is evident that genetics does play a role in susceptibility, someone with questionable genetics should not consider AD an inevitable event. Powerful environmental factors (which are obviously more controllable) can play a great role to protect against genetic weakness. By minimizing exposure to toxins like aluminum, silicon, neurotoxins (drugs that affect the brain and nervous system), and by maintaining high levels of antioxidants, genetic weakness could be nullified.