Understanding risk factors for Parkinson's disease is a big priority for MJFF. Not only does it better inform patients and families about the cause and diagnosis of the disease but it we believe it is essential information in the effort to improve treatments for PD. Without better understanding early PD and how PD progresses, we are hamstrung in developing disease modifying treatments.
Here is information on understanding Parkinson's disease which includes information on risk factors and what can be done to reduce risks of getting PD. Be sure to "open" the various FAQ's and you will get information on everything from "causes" to a "screening questionnaire".
Here is more information on genetic risk factors for Parkinson's disease.
Note that your Dad (and all PD patients) are entitled to a free lifetime membership at 23andMe. More here: https://www.23andme.com/pd/
Here is more information on living with Parkinson's disease, which included information on
Hope this helps...