Every parent can give anecdotal evidence of how one or more of their children exhibited specific traits from birth. Now science is starting to give credence to these statements. Scientists are uncovering genes that correlate with certain behaviors and tendencies. These studies are still in their early days, but it appears that more and more research is going to confirm a biological basic behvior.
Biology =/= Genetics. Biology is just how organisms are structured. When people in everyday life speak to us and show us things that sends signals through our eyes and ears to the brain. So biological is not distinct from cultural or environmental or social influence. Yet people often mistakenly treat these as though they were separate. For example people assume if there is a difference in brain chemistry it automatically means genetics, but there's no reason for the sound waves and light waves others make that come into our brains and interact with our memories over long periods of time wouldn't have an influence. In fact there's no good reason to assume that the choices that we make on a daily basis with how we choose to approach things in our lives and how we choose to think about and view the world would not have an influence. It makes more sense if you think about it that that clearly WOULD have influence. Your own thoughts, your own actions, your own choices DO have an affect upon your own biology especially within the brain.
It could be argued that everything that makes up a person has some sort of link or factor tracing back to the genetics of that person. As modern science techniques develop, we are finding more about our genome that factors into personality. We've even found some potential proof that there is a genetic basis for determining the sexuality of an individual! Although a gene may not ultimately decinde things like "what music you like" or "your favorite foods", there is definitely some sort of predisposition that stems from the gene pool.
All our emotions are based on our brain's chemical response to stimulus. How we react is a result of that response plus our brain's unique anatomy which we call a personality. Any personality trait, no matter how strange, is a response to a chemical change in the brain which are so familiar to us that we call them human nature.
Some personality traits can be based on biology. Brain chemistry, DNA and hormonal balances can shift thanks to several factors. However, some personalities develop thanks to experience and learning. How we learn and the experiences we undergo can also have a biological basis. Someone with certain biological traits may have different life circumstances, and hence go through different experiences, than others. Some personalities are inherent, but others come from experience and observation.
I think there is some biological basis, but it's not the only factor. People are shaped by their DNA, but also by their environment. Certain people may be predisposed to certain traits due to their ancestry, however, I believe that environment is equally (if not more) important in shaping one's personality. It's important to consider nurture as well as nature, in other words.