Many people see the conflicts between the belief that God is in control of everything and the belief that a set of rules called Science is in control of everything. These two beliefs do not need to conflict: God created the world (Genesis 1-2), and in creating it he set up certain rules that the His creation would follow. Your statement of genes and chemicals determining specific traits is a good example of this - note that in the creation narrative, each thing is said to be "according to it's kind" (1:21, 24, 25). God got creative and picked out the genes for each animal, then put them all together and decided that those genes would keep each animal reproducing "according to it's kind." In other words, a duck won't hatch a cow, but only a duck, and the duck it hatches will resemble the parents to an extent. All of nature is guided by similar rules which God set up when he created it. God set the rules in place which gave certain genes in your parents and mixed their genes to make yours. The extent to which these genes determine personality is still a topic of much debate, as environmental factors are also an influence. But once again, God is in control of those environmental factors, too.

Think of a play you've seen. You could say that the play is the way it is because the author wrote it that way. Or you could say it's because the director chose to use the piece in a certain manner. Or you could say that it's because the actors and actresses are doing their thing. Any way you look at it, you're right, because each of these elements has a varying degree of control concerning the outcome, yet each of these elements is subject to the one before, with the exception of the author. Similarly, God wrote the rules, Science carries out the rules, and we, as humans, are subject to the rules, but also have a free choice to change that which the rules leave flexible.