  A fermion mass matrix ansatz is proposed in the context of Grand Unified
Supersymmetric Theories (GUTs). The fermion mass matrices are evolved down to
the electroweak scale by solving the renormalization group equations for the
gauge and Yukawa couplings. Eight inputs are introduced at the GUT scale to
predict the 13 arbitrary parameters of the Standard model. The constraints
imposed by the charged fermion data are used to make predictions in the
neutrino sector. In particular, the neutrino mass matrix is worked out in the
case of the flipped SU(5) model and it is found that the
  {\it generalized } see-saw mechanism which occurs naturally in this model can
provide a solution to the solar neutrino puzzle and give a sufficiently large
$\nu_{\tau}$ mass to contribute as a hot dark matter component as indicated by
the recent COBE data.
