"Human values: Genetic and environmental effects on five lexically derived domains and their facets"
By Walter Renner et al.
Whereas a substantial genetic component of Conservatism and Religiosity is well documented, there is little evidence with respect to the behavior genetics of other aspects of human values. A sample of 157 monozygotic and 74 dizygotic twins reared together received the Austrian Value Questionnaire (AVQ), which measures a broad variety of value domains and their facets, found by the lexical approach in the German language. Family resemblance of Intellectualism, Harmony, Materialism, and Conservatism was best explained by additive or dominance genetic and non-shared environmental effects, whereas the influence of the environment shared by twins was negligible. In contrast, Religiosity was transmitted by additive genetic, shared and non-shared environmental influences. At the level of facets, the Intellectualism and Harmony showed a homogenous etiology while Religiosity, Materialism, and Conservatism were etiologically heterogeneous.
Personality and Individual Differences. In Press, Corrected Proof - doi:10.1016/j.paid.2011.09.003
Aren't you glad that there's someone around to translate that academic Double-Dutch for you?
Note initially that after decades of research it is now generally accepted that both political and religious ideology is substantially determined by your genes. You didn't CHOOSE to be a Conservative or religious: You were BORN that way. That still grates on the teeth of most people but that is what the inheritance research has repeatedly shown. Exactly WHAT is inherited which makes you a Leftist is still not pinned down but my bet is that it is a tendency to be miserable. Happiness is definitely a stable trait and conservatives are certainly happier, which again shows up repeatedly in research.
But that is all prelude. The reseachers above were looking for OTHER things that might be genetically inherited. They found that traits of Intellectualism, Harmony, Materialism, and Conservatism were all determined heavily by genetics but hardly at all by the environment. Religiosity, however, was to a degree influenced by your environment. Pretty simple, really -- even if runs against almost everybody's preconceptions.
You now see why elections are won or lost according to how well the candidate appeals to the voter in the middle. Most of us are born conservative (happy) or Leftist (miserable) and can't be changed from that. It's only the minority who are half way between happy and miserable who can be swung. Background on previous research in the area here
Clarifying note: It is your tendency to be religious in general that is inherited, not your particular religion.