  We provide a complete calculation of all leading nucleon form factors at
large momentum transfer and in single gauge boson exchange approximation. In
order to evaluate the required nucleon transition probability matrix elements,
we combine QCD perturbation theory with an expansion in nucleon distribution
amplitudes. Using leading twist nucleon distribution amplitudes only, one
obtains the desired nucleon form factors. The obtained results are consistent
with experimental data when we use third order polynomials for the distribution
amplitudes and non-perturbative models for the coefficients. Finally, we
compare our results for the Dirac form factor of the proton with previous
results based on the QCD factorization theorem, where a discrepancy about the
correct symmetry factor is still under discussion. We examine the calculations
and propose an explanation.
