We study the nucleon structure function ${F}_{2}$ for deep-inelastic scattering of leptons on an isoscalar target. The Owens-Reya parton distributions with charm added give good agreement with the data up to ${Q}^{2}\ensuremath{\sim}100$ GeV for the case of no color production. If color is produced, we describe in detail what effect this would have on ${F}_{2}$ to leading nontrivial order in Pati-Salam quantum chromodynamics with massive gluons.