This topic always sparks a lot of discussions. It is one question that is really important to both - religious or scientific. We can reformulate it as follows: how much is personality of a human inborn and how much is accumulated through life? What can be inborn and what cannot? (By inborn I mean something that is independent of environment)
It is really a difficult question and cannot be answered precisely by scientists because of the following reason: you cannot make experiments (you cannot rise the same child in one environment, change it, and make experiments again). Anyway, some assumptions can be made using just simple logics. Of course, you can make experiments with twins and this way you could get more precise results, but when it comes to human - you cannot ignore human rights. So today non-scientific cummunity speaks about various stuff that is inside human being from the beginning and that is just because science respects human rights and does not sacrifice them to make experiments. So science can't tell you exactly - that's why people speak out of their imagination and personal experience.
I really dislike when people speak about something they don't know with so much confidence - first of all - admit you don't know, don't be afraid to be ignorant - that is much better than argueing about something you have no idea about. The question of this topic is really broad - it includes many subjects: genetics, neuralscience, biology, sociology (human-world and human-human interaction), statistics, psychology, early-age brain formation, etc., etc. So why do you say that you got the right answer to it?
According to my knowledge (which is always not precise and incomplete): a human is formed from two cells (egg and sperm - 100% truth). I may ask - how much information can you carry inside these two cells? The answer is DNA - everything that is inborn can be told by looking at this double helix molecule. If mother smokes/uses drugs - she damages your development inside her tummy, so the changes you get are not inborn, and if you examine inborn features only after 9 months - you are making a mistake. But anyway, these all are connected to probability to get some disease but not to personality.
What about personality? Is there something inside you which senses what is good and what is bad, is it inborn? I strongly doubt it, because this good/bad sense is so complex and so arbitrary, DNA cannot have such luxury and have this encoded inside itself. DNA is just a code which tells what proteins to make, so it says "how are you made" and not "how is the outside world made, what are the relationships between outside world objects".
I must apologize, but this question is so broad that you can write tens of books and still don't grasp it's meaning. I have some duties to do in my real world... I will return to it from time to time resolving main questions: what is encoded inside DNA? what makes us humans? how does brain works? etc.