  A symmetry violation model is considered for a system that can spontaneously
choose between identical states which differ from each other only in weak
properties (R-L). Such mirror symmetry allows reproduction of observed
qualitative properties of quark and lepton mixing matrices. The lepton mixing
matrix evidences in this case in favor of the inverse mass spectrum and the
Dirac nature of SM neutrino. Notwithstanding the Dirac properties of neutrino,
an exchange of lepton numbers such as $e^{-}+\mu^{+}\rightarrow e^{+}+\mu^{-}$
is possible but with only leptons participating in the process.
