The discovery and documentation of genetic factors and environmental exposures for family members may facilitate developing targeted treatment of PD and possibly identify preventive treatment alternatives.
Parkinson Disease Overview -- A good place to start, it Is updated periodically
Genetics of PD -- Explains the Science of Parkinson's; also see this article
Promethease -- Compares your genetic data (as from 23andme) to a database of possible medical conditions
Genetic vs. Idiopathic -- Are genetic and idiopathic forms of Parkinson's disease the same disease?
Parkinson's and SNPedia -- Brief, but many links to details
Missing Heritability In PD Genetics may be more important than historically considered
"The cause of most cases of Parkinson’s disease is unknown. While researchers have established that both hereditary and environmental factors influence a person’s risk for developing Parkinson’s, for the most part, they don’t know why some people get Parkinson’s and some people don’t. Most scientists believe Parkinson’s is most likely caused by a combination of inherited and environmental factors." My Parkinson's Team
A caution -- Genetic testing may cover selected genes. 23andme, as an example, only addresses variations related to LRRK2 and GBA. You can obtain additional information by running your 23andme data through Promethease .
Ask your doctor about genetics testing by a service such as GeneDx that provides medical grade testing.