The debate between nature versus nurture is one which influences nearly every field, from biology to sociology. The essential question of whether we are "born" or "made" the way we are has never fully been answered, but perhaps personality theory is the mirror-theory that can be used to understand the debate.
Personality theory states that we are genetically prone to a myriad of possible behaviors. We get bits and pieces basically from every potential genetic mutation and mix that there is in your genealogy tree. Your unique personality is what will displays all the genetic dispositions that you are prone to exhibit. Therefore, when a situation occurs, the actions, reactions and interactions that you as an individual display automatically are inherent to your unique personality. In not so many words, you act out what you are. That is the genetic answer.
However, when the actions, reactions, and interactions that you engage into are not beneficial to you (they make you wild, dangerous, or out of place), then you can recognize those actions and transform them to fit a new scenario- that is the environmental answer. The actions have not disappeared; they are part of your genetic make up. Just like some diseases are prone to your genetic make up. However, they do not need to manifest unless they are triggered....by the environment!
The best example is alcoholism. Since it is considered an addictive disease, people with a family history of alcoholism are told always to remember that they have a genetic pre-disposition to become alcoholics. However, if they never taste it, or buy it, or even look at it....will they be alcoholics? Only when the environment presents optimal settings for the genetic behavior to display. Hence, if it is not there, the behavior will not manifest even though it is lurking beneath the surface.
Therefore: genetics precede the environment. The environment definitely trigger genetics. According to personality theory, the interactions with the environment is what defines whether the genetics will manifest or not.
Read Gordon Allport and theory of personality for more information.