Evaluation of the isospin asymmetry of the nucleon structure functions with CLAS++

The possibility to estimate the isospin symmetry breaking effects in the non-perturbative part of F_2 structure function of the chargeg lN deep-pnelastic scattering, which will provide CLAS++ dewtector of the upgraded TJNAF machine at $Q^2\approx 2Ge{V}^2$, is discussed. The problems of the Gottfried sum rule extraction are also considered.