  Efforts to unify group-theoretically the standard-model gauge interactions
with the generation structure of fermions and their mirror partners should be
accompanied with the unification of the corresponding gauge couplings. In this
paper the possibility of such a unification is studied and conclusions on
possible symmetry-breaking channels and scales, as well as on the fermion
content of the theory, are drawn. The breaking of some of the symmetries allows
various Majorana masses for neutrinos and their mirror partners, so these are
studied next. Implications to neutrino mixings and mass hierarchies in
connection with recent experimental results, as well as to electroweak
precision tests, are then discussed.
