The process of finding new genes that might be causing Parkinson’s or other conditions is disease gene discovery. There are a variety of approaches for identifying genes:
- Candidate gene approach: genes are selected based on their known or predicted biological function and on their hypothesized relation to the disease or trait.
- Family-based segregation: this involves comparing an individual with the condition and their relatives, some of whom may also be affected by the condition. By comparing people in a family who have the condition to people who do not have the condition, researchers can look for gene changes that occur in affected but not unaffected family members. These studies can help to identify rare, high-risk disease-causing genes.
- Association studies: Large research projects, known as Genome-Wide Association Studies (GWAS), are used to identify genes that increase susceptibility to developing a condition. A GWAS involves comparing genetic variants in thousands of people with a particular condition with those who do not have the condition. The goal is to identify areas of the genome that are ‘associated’ with the condition and then to look in those areas to find genes that may increase susceptibility to, or give protection from, the condition. These can be helpful in identifying lower-risk but more common disease-causing genes.