Do a search for [genetic basis for introversion] and you'll find articles like this:
Social Introversion-Extraversion as a Heritable Response
As for the functions, there is no scientific evidence to support their existence. Or even a coherent hypothesis. You would first have to identify brain differences (if any), then identify the genes responsible for those differences in order to establish a genetic basis for type.
Yeah. Not gonna happen any time soon.
Looking at arbitrary sets of data and hunting for patterns isn't really going to yield anything useful. Too many variables.
There is another thread somewhere where this sort of data was collected but I couldn't find it.