  We consider a model with anomaly-free Abelian gauge axial-vector symmetry,
which is intended to mimic the standard electroweak gauge chiral SU(2)_L x
U(1)_Y theory. Within this model we demonstrate: (1) Strong Yukawa interactions
between massless fermion fields and a massive scalar field carrying the axial
charge generate dynamically the fermion and boson proper self-energies, which
are ultraviolet-finite and chirally noninvariant. (2) Solutions of the
underlying Schwinger-Dyson equations found numerically exhibit a huge
amplification of the fermion mass ratios as a response to mild changes of the
ratios of the Yukawa couplings. (3) The `would-be' Nambu-Goldstone boson is a
composite of both the fermion and scalar fields, and it gives rise to the mass
of the axial-vector gauge boson. (4) Spontaneous breakdown of the gauge
symmetry further manifests by mass splitting of the complex scalar and by new
symmetry-breaking vertices, generated at one loop. In particular, we work out
in detail the cubic vertex of the Abelian gauge boson.
