Here are some really easy to read sources on the genes that contribute to FAD (Familial Alzheimer's Disease) PSEN1, PSEN2, and AAP for anyone looking for a brief but concise overview of what each gene does normally, what kind of mutations it undergoes, and what occurs on the physical level as a result:
Genetics Home Reference: PSEN1. 2011 Feb 27. <http://ghr.nlm.nih.gov/gene/PSEN1>. Accessed 2011 Mar 3.
Genetics Home Reference: PSEN2. 2011 Feb 27. <http://ghr.nlm.nih.gov/gene/PSEN2>. Accessed 2011 Mar 3.
Genetics Home Reference: AAP. 2011 Feb 27. <http://ghr.nlm.nih.gov/gene/APP>. Accessed 2011 Mar 3.