  Adjoint supermultiplets (1,3,0) and (8,1,0) modify the evolution of gauge
couplings. If the unification of gauge couplings occurs at the string scale,
their masses are fixed at around $10^{13}$ GeV. This scale coincides with
expected gaugino condensation scale in the hidden sector $M_{string}^{2/3}
m^{1/3}_{3/2} \sim 10^{13}$ GeV. We show how neutrino masses arise in this
unified model which naturally explain the present atmospheric and solar
neutrino data. The out-of-equilibrium decay of the superfield (1,3,0) at
$10^{13}$ GeV may also lead to a lepton asymmetry which then gets converted
into the present observed baryon asymmetry of the Universe.
