And, given the availability of new molecular techniques, one ought to expect substantially more observations of this kind in the years to come. In the face of that, what needs to be kept in mind is that the observations show that genes influence personality. They do not, and cannot show that genes determine personality. Even many scientists tend to confuse the two sorts of conclusions, presuming that an observation showing something to be influenced by one thing necessarily implies that other things are irrelevant. This is simply not the case.
Genes do influence personality, as they do intelligence and every other aspect of being human.
What they don't do, for personality or any other aspect of being human, is to determine it . Not only environmental influences but also personal dreams and choices demonstrably play a role as well. The citations in this response are part of a website maintained by myself and a group of colleagues as a resource for people interested in brain, behavior and education.