  A full account is given of the procedure used by the authors to construct an
SO(10) supersymmetric grand unified model of the fermion mass matrices. Various
features of the model which gives remarkably accurate results for the quark and
lepton masses and mixings were presented earlier in separate publications. The
construction of the matrices is first discussed in the framework of effective
operators, from which one naturally obtains the maximal \nu_\mu - \nu_\tau
mixing, while the small angle or maximal mixing solutions for the solar
neutrinos depend upon the nature of the Majorana matrix. A set of Higgs and
fermion superfields is then introduced from which the Higgs and Yukawa
superpotentials uniquely give the structure of the mass matrices previously
obtained. The right-handed Majorana matrix arises from one Higgs field coupling
to several pairs of superheavy conjugate neutrino singlets. For the simple
version considered, 10 input parameters accurately yield the 20 masses and
mixings of the quarks and leptons, and the 3 masses of the right-handed
neutrinos.
