Final answer:
The first known predisposing allele for common, late-onset Alzheimer's disease is the E ApoE ε4 variant. It's part of the apolipoprotein E (APOE) gene and enhances the risk of developing the disease. Additional research continues to identify other contributing genetic factors.
Step-by-step explanation:
The first known powerful, predisposing allele for common, late-onset Alzheimer disease among the options provided is E ApoE ε4. This allele is found in the apolipoprotein E (APOE) gene which has a variant known as E4 that significantly increases a person's risk of developing Alzheimer's disease. It's important to note that the relationship between APOE ε4 and Alzheimer's is complex and not fully understood, but carrying this allele is recognized as a major genetic risk factor for the late-onset form of the disease.
There have been other genes identified that might contribute to the pathology of Alzheimer's disease, and ongoing research continues to expand our understanding of the genetic components involved. For example, a study in April 2011 discovered five new genes associated with increased Alzheimer's disease risk in the elderly, offering additional insights into the genetic underpinnings of the condition.