  A new SO(10) unified model is proposed based on a one step breaking of SO(10)
to the Standard Model gauge group $SU(3)\times SU(2)\times U(1)_Y$ using a
single 144 of Higgs. The symmetry breaking occurs when the SU(5) 24-plet
component of 144 develops a vacuum expectation value. Further, it is possible
to obtain from the same 144 a light Higgs doublet necessary for electro-weak
symmetry breaking using recent ideas of string vacua landscapes and fine
tuning. Thus the breaking of SO(10) down to $SU(3)_C\times U(1)_{em}$ can be
accomplished with a single Higgs. We analyze this symmetry breaking pattern in
the nonsupersymmetric as well as in the supersymmetric SO(10) model.In this
scenario masses of the quarks and leptons arise via quartic couplings. We show
that the resulting mass pattern is consistent with experimental data, including
neutrino oscillations. The model represents an alternative to the currently
popular grand unified scenarios.
