  Group theoretical factors from GUT symmetry breaking can lead to predictions
for the ratios of quark and lepton masses (or Yukawa couplings) at the
unification scale. Due to supersymmetric (SUSY) threshold corrections the
viability of such predictions can depend strongly on the SUSY parameters. For
three common minimal SUSY breaking scenarios with anomaly, gauge and gravity
mediation we investigate which GUT scale ratios $m_e/m_d$, $m_\mu/m_s$,
$y_\tau/y_b$ and $y_t/y_b$ are allowed when phenomenological constraints from
electroweak precision observables, $B$ physics, $(g-2)_\mu$, mass-limits on
sparticles from direct searches as well as, optionally, constraints from the
observed dark matter density are taken into account. We derive possible new
predictions for the GUT scale mass ratios and compare them with the
phenomenologically allowed ranges. We find that new GUT scale predictions such
as $m_\mu/m_s = 9/2$ or 6 and $y_\tau/y_b = 3/2$ or 2 are often favoured
compared to the ubiquitous relations $m_\mu/m_s = 3$ or $y_\tau/y_b =1$. They
are viable for characteristic SUSY scenarios, testable at the CERN LHC and
future colliders.
