A gene "for" x simply means something like the existence of a genetic basis that would, if all other factors remain constant, make it statistically more likely for an organism to exhibit the phenotypic trait x. It does not mean that genes completely determine the phenotype or that one gene always corresponds to one phenotypic trait or that one phenotypic trait is necessarily caused by a single gene.
You can investigate the heritability of something by twin studies. Identical twins raised together share genes and environment. Differences between identical twins are mostly random. Identical twins raised apart share genes, but not environment, thereby provided a way to reduce many environment factors such as upbringing as a causal factor for whatever it is you are studying.
One interesting study that was published in Science back in 2008 suggested that there http://www.sciencemag.org/cgi/content/abstract/sci;321/5896/1667 (
full text).
The authors suggest that "[...] political attitudes and varying physiological responses to threat may both derive from neural activity patterns, perhaps those surrounding the amygdala. There is a connection between localized activation of the amygdala and aversive startle response. Amygdala activity is also crucial in shaping responses to socially threatening images and may be connected to political predispositions. Indeed, given that political and social attitudes are heritable and that amygdala activity also has been traced to genetics, genetic variation relevant to amygdala activity could affect both physiological responses to threat and political attitudes bearing on threats to the social order."
So to answer your question, yes, interests and beliefs are probably in many cases indirectly influenced by genes, but environment is important for shaping these influences.