  Right-handed (RH) rotations do not play a role in the Standard Model, and
only the differences of the LH mixing angles are involved in ${\bf V}_{\scr
\textrm{CKM}}$. This leads to the huge freedom in the fermionic mass matrices.
However, that is no more true in extensions of the Standard Model. For example
in GUTs large RH rotations of the quarks can be related to the observed large
neutrino mixing or in particular, all mixing angles are relevant for the proton
decay. We present a simple realistic non-SUSY SO(10) GUT with large RH and LH
mixing and study the corresponding nucleon decay rates.
