Majorana neutrino masses and lepton mixing angles in the perturbative and semiempirical approach

Using the Wolfenstein parametrization of the Kobayashi-Maskawa matrix and empirical quark and charged-lepton masses, both expressed in powers of λ=sin${\theta }_C$, the mass ratios of Majorana neutrinos and the lepton mixing angles are obtained with the aid of an SO(10)-motivated model for fermion mass matrices. A lower bound of 42 GeV on the top-quark mass is also obtained.