Several genes. There is a very active effort to find genetic causes of parkinson's disease. There is a research study called progeni that has more information on the site. Http://progeni. Iu.edu currently the genes associated with parkinson's are alpha-synuclein (snca) & lrkk2 for dominant inheritance and parkin, pink1 & dj-1 for recessive inheritance.
Couple points. As a consequence of our genetic data, we are starting to find patterns of susceptibility to various neurological disorders, and even starting to appreciate eventual outcomes. This will help with prognosis and even perhaps pinpoint more specific medications. This of course does apply to Parkinson's which is not a true genetic disorder.
Much, much more. The discovery of the genes associated with the diseases and how they cause them has caused a revolution in our approach to therapy, from chance testing to see if something helps. To understanding the primary problem and then being able to create a key that fits the keyhole of the problem.