Previous studies have found that both political orientations (Alford, Funk, & Hibbing 2005) and voting behavior (Fowler, Baker & Dawes 2007, Fowler & Dawes 2007) are significantly heritable. In this article we study genetic variation in another important political behavior: partisan attachment. Using the National Longitudinal Study of Adolescent Health, we show that individuals with the A1 allele of the D2 dopamine receptor gene are significantly less likely to identify as a partisan than those with the A2 allele. Further, we find that this gene’s association with partisanship also mediates an indirect association between the A1 allele and voter abstention. These results are the first to identify a specific gene that may be responsible for the tendency to join political groups, and they may help to explain correlation in parent and child partisanship and the persistence of partisan behavior over time.
And here is the paper itself.