  Extensions of the Standard Model with additional U(1) symmetries can describe
the hierarchy of fermion masses and mixing angles, including neutrinos. The
neutrino masses and mixings are determined up to a discrete ambiguity
corresponding to the representation content of the Higgs sector responsible for
the Majorana mass matrix. The solar and the atmospheric neutrino deficits as
well as the COBE data, may be explained simultaneously in specific schemes
motivated by symmetries. Using simple, analytic expressions, it is possible to
demonstrate the known effect that for small $\tan\beta$, phenomenologically
interesting neutrino masses would disturb the bottom-tau unification. This
however can be avoided in schemes with a large $\mu-\tau$ mixing in the charged
leptonic sector. On the other hand, for the large $\tan\beta$ regime, due to
the fixed point properties of the top as well as the bottom coupling (which are
described by analytic expressions, for sufficiently large couplings) no
modification to the bottom-tau unification would occur. Still, large mixing in
the $\mu$-$\tau$ sector is desirable in this case as well, in order to have a
solution to the atmospheric neutrino problem. In the same schemes, a relatively
heavy strange quark $\approx 200$ MeV is also predicted.
