  The unpolarized, helicity and transversity parton distribution functions of
the nucleon are studied within a convolution model where the bare nucleon is
dressed by its virtual meson cloud. Using light-front time-ordered perturbation
theory, the Fock states of the physical nucleon are expanded in a series
involving a bare nucleon and two-particle, meson-baryon, states. The bare
baryons and mesons are described with light-front wave functions (LFWFs) for
the corresponding valence-parton components. Using a representation in terms of
overlap of LFWFs, the role of the non-perturbative antiquark degrees of freedom
and the valence quark contribution at the input scale of the model is discussed
for the leading-twist collinear parton distributions. After introducing
perturbative QCD effects through evolution to experimental scales, the results
are compared with available data and phenomenological extractions. Predictions
for the nucleon tensor charge are also presented, finding a very good agreement
with recent phenomenological extractions.
