I certainly feel I would not be the same persomn I am today if it were not for the the things which have happened to me. It seems all too obvious that my environment shaped me. I cannot think of a particular evidence that suggests I am shaped by my genes.
But surely it is a mixture of the two. I understand that I will react in a particular way to certain situations because of my genes. But it is that situation which will alter my personality. We all started out shaped by our genes but the older we get the more we are shaped by circumstance.
However I do believe we can not be changed by our environment so far that we break our genetics. Our personality will always be bound by the rules our genes hold us to.