  A new procedure proposed recently enables one to start from the quark and
lepton mass and mixing data at the low scale and construct mass matrices which
exhibit simple SO(10) structure at the SUSY GUT scale. We elaborate here on the
numerical details which led us to an SO(10) model for the quark and lepton mass
matrices that explain the known quark data at the low scale along with the
observed depletions of solar- and atmospheric-neutrinos. We also apply the
procedure to a second scenario incorporating the solar-neutrino depletion and a
7 eV tau-neutrino for the cocktail model of mixed dark matter but find the
SO(10) model deduced in this case does not exhibit as simple a structure as
that observed for the first scenario.
