  A quantitative understanding of the weak nuclear response is a prerequisite
for the analyses of neutrino experiments such as K2K and MiniBOONE, which
measure energy and angle of the muons produced in neutrino-nucleus interactions
in the energy range $0.5-3$ GeV and reconstruct the incident neutrino energy to
determine neutrino oscillations. In this paper we discuss theoretical
calculations of electron- and neutrino-nucleus scattering, carried out within
the impulse approximation scheme using realistic nuclear spectral
functions.Comparison between electron scattering data and the calculated
inclusive cross section off oxygen, at beam energies ranging between 700 and
1200 MeV, show that the Fermi gas model, widely used in the analysis of
neutrino oscillation experiments,fails to provide a satisfactory description of
the measured cross sections,and inclusion of nuclear dynamics is needed.
