Realistic quark and lepton masses through SO(10) symmetry

A model of quark and lepton masses based on SO(10) symmetry is presented. Almost all qualitative and quantitative features of the quark and lepton masses and the quark mixing angles are explained as consequences of various aspects of SO(10) invariance without any family symmetry. The threefold mass hierarchy as well as the phenomenologically successful relations m0τ ≅ m0b, m0μ ≅ 3m0s, m0c ≅ 1/3m0d, m0u/m0t << m0d/m0b, tanθC ≅ √(m0d/m0s), Vcb << √(m0s/m0b) and Vub ∼ VusVcb follow from a simple Yukawa structure at the unification scale. The model has predictions for tanβ, proton decay branching ratios and neutrino mixing angles. (orig.)