Quantum Electrodynamics (QED): the basic interaction vertex
Quantum Chromodynamics (QCD): the basic interaction vertex
The Weak Force: the basic interaction vertices
The fundamental charged vertex couples a W with an up-type quark and a down-type quark. The up-type and down-type quarks can come from different generations, i.e. u with s, d with c, or c with b. The allowed amount of cross-generational coupling is determined by the Cabibo-Kobayashi-Maskawa (CKM) matrix.
The picture is that the quarks that form hadrons are mass eigenstates, while what couples to the W and Z are the weak eigenstates, and for the quarks the two are not lined up. By convention we choose our phase such that the up-type quarks have no mixing between mass eigenstates and weak eigenstates. Then the weak eigenstates of the down-type quarks are linear combinations of the mass eigenstates given by:
Some additional diagrams are needed to complete the electroweak theory. The two most important are the WW