  We investigate the predictions for various nucleon decay rates and their
ratios in non-supersymmetric SU(5) Grand Unified Theories (GUTs) where the
masses of the third and second family down-type quarks and charged leptons each
stem dominantly from single GUT operators. Extending the Georgi-Glashow SU(5)
model by a 45-dimensional GUT-Higgs representation, the gauge couplings can
meet at the high scale $M_\mathrm{GUT}$ and the GUT scale predictions
$y_\tau/y_b = 3/2$ and $y_\mu/y_s = 9/2$ can emerge within single operator
dominance. Explaining the observed neutrino masses via the type I seesaw
mechanism by adding SU(5) singlet fermion representations and taking their
renormalization group effects into account, we show that these predictions can
lead to viable low scale second and third family down-type quark and charged
lepton masses. To investigate nucleon decay predictions, we extend the minimal
scenario to two "toy models" towards explaining quark and lepton masses and
mixings with different flavor structure, and perform Markov Chain Monte Carlo
(MCMC) analyses confronting the models with the available experimental data. We
show that if several nucleon decay channels are observed, the ratios between
their partial decay rates can serve as "fingerprints", allowing to separate
between GUT models with different flavor structure.
