  The gauge-boson, ghost and fermion propagators as well as the
gauge-boson--ghost vertex function are studied for SU(N), Sp(2N) and SO(N)
gauge groups. We solve a set of coupled Dyson-Schwinger equations in Landau
gauge for a variable, fractional number $N_f$ of massless fermions in the
fundamental representation. For large $N_f$ we find a phase transition from a
chirally broken into a chirally symmetric phase that is consistent with the
behavior expected inside the conformal window. Even in the presence of fermions
the gauge-boson--ghost-vertex dressing remains small. In the conformal window
this vertex shows the expected power law behavior. It does not assume its
tree-level value in the far infrared, but the respective dressing function is a
constant greater than one.
