Sure, I think I can help. You’re right about how if you have a gene for something and it doesn’t happen, like having a high change for breast cancer, and it doesn’t occur, you wouldn’t say you have it. This is the difference between what they call phenotype and genotype. Genotype is the actual presence in your DNA/genetics of something, let’s say Type II diabetes. Phenotype is how the gene is actually expressed in your life. So, let’s say you never eat sugar and only eat whole grains. That diabetes gene may never express itself then.
Traits are believed to be highly biological according to research. Twin studies (which is where we get all of this research) show that when twins are raised apart, often through adoption or some other situation, when they are tested later on, their traits of things like introversion/extroversion are nearly always matched. There are considered to be five core traits, which are called, “The Big Five.” They are 1) introversion/extroversion, 2) conscientiousness, 3) openness to experience, 4) agreeableness, and 5) neuroticism.
Personality psychologists have spent a lot of time studying the Big Five, and the consensus is that there is a lot of biology at play in determining these traits. As to psychopathy and sociopathy, there is a lot of argument about how much is biological, but we definitely see that a lot of people with these problems are affected by negative environmental influences. It doesn’t even have to be abuse per se. It could be just being raised in an emotionally cold home or having attachment issues at birth. That one’s tricky.