Final answer:
Alzheimer's disease (AD) related APP gene mutations do not occur in genes encoding alpha, beta, or gamma secretase. Mutations in the APP gene itself disrupt APP's normal processing by these secretase enzymes, leading to amyloid beta plaque formation.
Step-by-step explanation:
AD causing APP gene mutations refer to mutations in genes that affect the processing of amyloid precursor protein (APP), leading to the development of Alzheimer's disease. These mutations are not found in genes encoding alpha, beta, or gamma secretase enzymes directly. Rather, mutations within the APP gene itself can result in the aberrant processing of APP by these secretase enzymes, leading to the formation of amyloid beta (Ab) peptide, which can aggregate into plaques and contribute to neuronal degeneration and the onset of Alzheimer's disease symptoms.
Mutations in the APP gene are one of the known genetic factors for early onset Alzheimer's disease, while other genes such as apolipoprotein E (APOE) with its E4 variant are associated with the more common late-onset form. The genetic interplay in Alzheimer's pathology is complex and is not limited to secretase enzymes' encoding genes.