2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/198645Assuming three light neutrinos and the see-saw mechanism we present a semiquantitative model of fermion masses based on (SUSY) SU(5) and abelian horizontal charges. A good description of the observed pattern of quark and lepton masses is obtained. For neutrinos we naturally obtain widely split masses and large atmospheric neutrino mixing as a consequence of SU(5)-related asymmetric mass matrices for d quarks and charged leptons.12 pages, LATEX, no figures; discussion added on the just-so solution; version to appear on Phys. Lett. BHigh Energy Physics - Phenomenologytext