  I analyze the predictions for the strong gauge coupling, $\alpha_3(M_Z) $,
and the top quark and light Higgs masses in the framework of gauge and
bottom-tau Yukawa coupling unification in the minimal supersymmetric standard
model. These predictions depend on the effective supersymmetric threshold scale
$T_{SUSY}$, which is only very slightly dependent on the squark and slepton
masses, and strongly dependent on the Higgsino masses as well as on the mass
ratio of the gauginos of the strong and weak interactions. Within the minimal
supersymmetry breaking scheme and for supersymmetric masses below or of the
order of 1 TeV, I obtain $\alpha_3(M_Z) \geq 0.116$, while, if the running
bottom quark mass at the physical mass is constrained to be $ m_b(M_b) \leq 4.1
$GeV, then, for moderate values of $\tan \beta$, perturbative unification is
achieved only if $\alpha_3(M_Z) \leq 0.124$. Unification of gauge and
bottom-tau Yukawa couplings yield predictions for the top quark mass, 140 GeV
$\leq M_t \leq 210 $ GeV for $1 \leq \tan \beta \leq 30$, which are remarkably
close to the infrared quasi fixed point values for this quantity. For the light
Higgs mass I obtain $m_h \leq 130(165)$ GeV if the characteristic squark mass
is below 1 (10) TeV.
