No one is sure or has been able to paint a clear picture of which one plays a larger role in the development and use of our mental abilities. Some feel the primary influence has a biological (nature) and others environmental (nurture).
The nature side of the debate argues that a person maintains their mental abilities and capabilities based on what they where born with and what is in their genetics. They feel that a person's surroundings and environment play little to no role. Factors that support this idea include parents, development, appearance and nutrition.
Others argue and state that a person's environment is responsible for mental capabilities. This may seem less obvious to some but a person is surrounded by many other people and ideas. A person's environment does play an important role from early on. As one grows up they are exposed to television, hero's, icons and peer pressure. .
All of these factors influence a vulnerable, young mind and may curve a person's way of thinking or how they feel about a certain topic. .
Even if it is never proven which one plays a larger role, it seems obvious that they both are important in shaping a persons behavior. Genes may influence your personality, which will in turn affect the way you behave. Genes alone don't determine who we are, you can possibly inherit opinions, beliefs and interests as you grow up. Life experiences also shape our personalities. A person growing up in a broken home may not turn out to be as biologically healthy then the kid who had both parents. .
Alcoholism it could be generated and passed on biologically or through the environment. For you might have knew someone growing up who might have had a grandparent or parent who was an alcoholic they may have tended to be the heavy drinkers at parties. This could lead a person to altered physical, mental and emotional states. These could be biological factors. I feel when it comes to alcoholism it tends to lean more toward environment.