  The NuTeV collaboration recently reported a value of sin2thetaW measured in
neutrino-nucleon scattering that is 3 standard deviations above the standard
model prediction. This result is derived assuming that (1) the strange sea is
quark-antiquark symmetric, s(x)=sbar(x), and (2) up and down quark
distributions are symmetric under the simultaneous interchange of u<->d and
p<->n. We report the impact of violations of these symmetries on sin2thetaW and
discuss the theoretical and experimental constraints on such asymmetries.
