  The quark and lepton mass patterns upset their naive unification. In this
paper, a new approach to solve this problem is proposed. Model-independently,
we find that a successful unification can be achieved. A mechanism is
identified by which the large top quark mass renders its third-generation
leptonic partner very light. This state is thus identified with the electron.
We then provide a generic dynamical implementation of this mechanism, using
tree-level exchanges of vector leptons to relate the quark and lepton flavor
structures. In a supersymmetric context, this same mechanism splits the squark
masses, and third generation squarks end up much lighter than the others.
Finally, the implementation of this mechanism in SU(5) GUT permits to avoid
introducing any flavor structure beyond the two minimal Yukawa couplings,
ensuring the absence of unknown mixing matrices and their potentially large
impact on FCNC.
