- In a large class of supersymmetric SO(10) and left-right models, requiring that the effective theory below the scale of (Formula presented) breaking be the MSSM implies partial Yukawa unification with (Formula presented) and (Formula presented) The same result also emerges in models with a horizontal (Formula presented) symmetry. As a result, at the tree level, these models lead to vanishing quark mixing angles. We show that the correct mixing pattern can be generated in these models at the loop level from the flavor structure associated with the supersymmetry breaking terms. We generalize the constraints on supersymmetric parameters from flavor changing neutral current (FCNC) processes to include several squark mass insertions and confirm the consistency of the scheme. The expectations of this scheme for (Formula presented) violating observables in the B meson system are quite different from the KM model, so it can be tested at the B factories. 1999 The American Physical Society.