The role of linkage studies for common diseases

Linkage analysis when applied to common diseases has had limited success in mapping the genes contributing to them. We present a genealogic approach a pplied to the relatively isolated population of Iceland. We use an affected s-only, allele-sharing method - which does not specify any particular inher itance model - implemented in the new statistical program, Allegro, which c alculates lod scores based on multipoint calculations. We describe how this approach has helped us to map a gene contributing to the common late-onset form of Parkinson's disease to statistical significance.