Grand Unification in particle physics is appealing for merging three of the four elementary forces into one at very high energies. Besides the corresponding unification of gauge couplings, Grand Unified Theories predict unified Yukawa couplings of quarks and leptons to a Higgs boson. Yukawa unification has been tested by measuring the fermion masses at today's particle colliders and found to hold for heavy, but to fail for light fermions. This work is a study of corrections to Yukawa unification from higher-dimensional operators in a supersymmetric model with SO(10) gauge symmetry. Due to the unification of down quarks and leptons the large flavour mixing measured in neutrino oscillations induces large flavour-changing neutral currents among down-type quarks. The resulting effects in kaon physics observables strongly constrain the flavour structure of Yukawa corrections.