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We obtain a relationship between the hierarchies of mixing angles and of masses pertinent to the Cabibbo-Kobayashi-Maskawa (CKM) quark mixing matrix and the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) lepton mixing matrix. Using this relationship, we argue that the more severe hierarchy of the charge-$frac{2}{3}$ quark masses requires that the CKM matrix be close to a unit matrix whereas the milder hierarchy of the neutrino masses allows the PMNS matrix to depart markedly from the CKM matrix and contain large mixing angles of the type that are observed.
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We give a general analysis of neutrino mixing in the seesaw mechanism with three flavors. Assuming that the Dirac and u-quark mass matrices are similar, we establish simple relations between the neutrino parameters and individual Majorana masses. They are shown to depend rather strongly on the physical neutrino mixing angles. We calculate explicitly the implied Majorana mass hierarchies for parameter sets corresponding to different solutions to the solar neutrino problem.
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