Subject: What creates charge on an elementary basis?

To be more precise what causes charge between elementary particles? If particles 
such as quarks are perceived to be elementary and therefore the smallest thing 
in existence, what causes them to be positive or negative? If there is a force 
acting upon the particles to create a charge and if so is it similar to the 
theory that gravity exists due to the exchange of gravitons? I am asking because 
I have an inquisitive mind and no-body I ask and knows and I can't seem to find 
an answer anywhere!

Re: What creates charge on an elementary basis?