  We propose a realistic model with Majorana neutrinos in the framework of
unifying the three generations of fermions by point interactions in an extra
dimension. This model can simultaneously explain the origin of fermion
generations, fermion masses and mixing, and the smallness of the masses of
Majorana neutrinos. We show that there are two mechanisms working together to
suppress the neutrino masses significantly, so we do not have to introduce a
very large extra-dimension cut-off scale. One is the type-I seesaw mechanism
and the other is the overlap integration of localized lepton wave functions. A
singlet scalar with an exponential-like VEV plays a central role in these two
mechanisms. For consistency in this model we introduce a $U(1)'$ gauge
symmetry, which will be broken by the singlet scalar. Parameters of our model
can fit the masses and flavor mixing data well. These parameters can also
predict all CP violating phases including the Majorana ones and accidentally
rescue the proton from decay.
