  A next-to-leading order QCD analysis of spin asymmetries and structure
functions in polarized deep inelastic lepton nucleon scattering is presented
within the framework of the radiative parton model. The $Q^2$-dependence of the
spin asymmetry $A_1^{p}(x,Q^2)$ is shown to be non-negligible for $x$-values
relevant for the analysis of the present data. In the second part of the paper
we present LO results for radiatively generated spin-dependent parton
distributions of the photon and for its structure function $g_1^{\gamma}$.
