  A model of symmetry violation is described for a system that can
spontaneously choose the left-handed or right-handed character of weak
currents. For the hierarchic structure of fermion mass spectra, such a mirror
symmetry system allows reproduction of all qualitative properties of weak
mixing matrices for both quarks (CKM matrix) and leptons (PMNS matrix),and at
that, without additional numerical fitting of model parameters. The hierarchy
of CKM matrix elements is directly stipulated by the hierarchical mass spectrum
of quark generations. The qualitative properties of the PMNS matrix arise for
the inverse character of the neutrino spectrum (m_3 is the smallest mass) and
Dirac nature of SM neutrino. The comparatively small value of the neutrino
mixing angle theta_13 is a consequence of the smallness of m_3 and the
smallness of the charged lepton mass ratio m_e/m_mu.
