  We take up the point of view that Yukawa couplings can be either 0 or 1, and
the mass patterns of fermions are generated purely from the structure of the
Yukawa matrices. We utilize such neutrino as well as charged leptonic textures
which lead to (maximal) mixing angles of $\pi/4$ in each sector for relevant
transitions. The combined leptonic CKM mixing angles are $\pi/4 \pm \pi/4$
which lead to very small $\sin^2 2 \Theta$ relevant to solar neutrino and LSND
experiments. We propose that on the other hand the absence of the charged
leptonic partner of the sterile neutrino maintains the angle $\pi/4$ from the
neutrino sector for the transition $\nu_\mu \leftrightarrow \nu_s$ and hence
atmospheric neutrino anomaly is explained through maximal mixing.
