  A form of mixing matrix for three active and three sterile, conventional
Majorana neutrinos is proposed. Its Majorana lefthanded part arises from the
popular bimaximal mixing matrix for three active neutrinos that works
satisfactorily in solar and atmospheric experiments if the LSND effect is
ignored. One of three sterile neutrinos, effective in the Majorana righthanded
and Dirac parts of the proposed mixing matrix, is responsible perturbatively
for the possible LSND effect by inducing one of three extra neutrino mass
states to exist actively. The corresponding form of neutrino mass matrix is
derived. If all three extra neutrino mass states get vanishing masses, the
neutrino mass matrix is dominated by its specific Majorana lefthanded part.
Then, the observed qualitative difference between mixings of neutrinos and down
quarks may be connected with this Majorana lefthanded dominance realized for
neutrinos.
