Is aggression bred? Or cultivated by circumstances? This question has been pondered for many decades, by many philosophers. One has to agree that there are certain breeds that are inherently more aggressive than others, for example, the pit-bull vs. the poodle. But if a pet grows up in a hostile and unhealthy environment, it is expected that the attention they know, is generated through negative reinforcement and just like any being, they will strive to make their presence known through aggression. Just like any human being, animals are products of their environment and the way they learned how to interact with others, by the way they were treated, formulates the type of relationships they cultivate.
So it is conclusive that while some characteristics are part of your genetic make-up, the emotions and personality traits that we all have can be encouraged to become prominent.